Ripgrep panicks when run with --word-regexp and empty string

[Emilv2]

What version of ripgrep are you using?

13.0.0

How did you install ripgrep?

Arch linux package manager

What operating system are you using ripgrep on?

Arch linux

Describe your bug.

Ripgrep panicks when run with --word-regexp and empty string.

What are the steps to reproduce the behavior?

For example, run in the ripgrep repository:

rg --word-regexp -- ''

What is the actual behavior?

DEBUG|grep_regex::word|crates/regex/src/word.rs:52: word regex: "(?:(?m:^)|\\W)((?:z{0})*)(?:\\W|(?m:$))"                                                                                  
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
DEBUG|globset|crates/globset/src/lib.rs:416: glob converted to regex: Glob { glob: "*", re: "(?-u)^[^/]*$", opts: GlobOptions { case_insensitive: false, literal_separator: true, backslash
_escape: true }, tokens: Tokens([ZeroOrMore]) }                                                                                                                                            
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 1 literals, 0 basenames, 0 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 1 regexes                               
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 1 literals, 0 basenames, 0 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                               
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 6 literals, 6 basenames, 2 extensions, 0 prefixes, 0 suffixes, 3 required extensions, 0 regexes                               
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
DEBUG|ignore::walk|crates/ignore/src/walk.rs:1741: ignoring ./.git: Ignore(IgnoreMatch(Hidden))                                                                                            
DEBUG|ignore::walk|crates/ignore/src/walk.rs:1741: ignoring ./.cargo: Ignore(IgnoreMatch(Hidden))                                                                                          
DEBUG|ignore::walk|crates/ignore/src/walk.rs:1744: whitelisting ./.github: Whitelist(IgnoreMatch(Gitignore(Glob { from: Some("./.ignore"), original: "!/.github/", actual: ".github", is_wh
itelist: true, is_only_dir: true })))                                                                                                                                                      
DEBUG|ignore::walk|crates/ignore/src/walk.rs:1741: ignoring ./.gitignore: Ignore(IgnoreMatch(Hidden))                                                                                      
DEBUG|ignore::walk|crates/ignore/src/walk.rs:1741: ignoring ./.ignore: Ignore(IgnoreMatch(Hidden))                                                                                         
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9                                                    
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace                                                                                                              
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9                                                    
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9                                                    
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9                                                    
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
DEBUG|globset|crates/globset/src/lib.rs:421: built glob set; 0 literals, 0 basenames, 12 extensions, 0 prefixes, 0 suffixes, 0 required extensions, 0 regexes                              
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9                                                    
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Any', crates/ignore/src/walk.rs:1302:31                                                                            
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9
thread '<unnamed>' panicked at 'assertion failed: self.start <= end', /build/ripgrep/src/ripgrep-13.0.0/crates/matcher/src/lib.rs:131:9
tests/data/sherlock.br

What is the expected behavior?

I'm not sure what the correct output would be since I'm not sure --word-regexp with an empty string makes sense, but certainly panicking isn't what I would expect.

[BurntSushi]

Duplicate of #1891, #2096