build: fix crash in pre-commit-hooks

[justincely]

Signed-off-by: Justin Ely justincely@gmail.com

Commit Message: add defensive coding against None in pre-commit hook
Additional Description: Fixes #16504
Risk Level: low
Testing: After fixing, was able to run git push and have the pre-commit hook spit out the right errors rather than python stacktrace.

Running pre-push check; to skip this step use 'push --no-verify'
  Checking format for tools/code_format/check_format.py - ERROR: Command clang-format-11 not found. If you have clang-format in version 10.x.x installed, but the binary name is different or it's not available in PATH, please use CLANG_FORMAT environment variable to specify the path. Examples:
    export CLANG_FORMAT=clang-format-11.0.1
    export CLANG_FORMAT=/opt/bin/clang-format-11
    export CLANG_FORMAT=/usr/local/opt/llvm@11/bin/clang-format
ERROR: Command None not found. If you have buildifier installed, but the binary name is different or it's not available in $GOPATH/bin, please use BUILDIFIER_BIN environment variable to specify the path. Example:
    export BUILDIFIER_BIN=`which buildifier`
If you don't have buildifier installed, you can install it by:
    go get -u github.com/bazelbuild/buildtools/buildifier
ERROR: Command None not found. If you have buildozer installed, but the binary name is different or it's not available in $GOPATH/bin, please use BUILDOZER_BIN environment variable to specify the path. Example:
    export BUILDOZER_BIN=`which buildozer`
If you don't have buildozer installed, you can install it by:
    go get -u github.com/bazelbuild/buildtools/buildozer

Docs Changes: None
Release Notes: None
Platform Specific Features: None
[Optional Runtime guard:]
[Optional Fixes #Issue]
[Optional Deprecated:]
[Optional API Considerations:]

[repokitteh-read-only]

Hi @justincely, welcome and thank you for your contribution.

We will try to review your Pull Request as quickly as possible.

In the meantime, please take a look at the contribution guidelines if you have not done so already.

🐱

Caused by: #16505 was opened by justincely.

see: more, trace.

[phlax]

hi @justincely i have a longer PR to address this here #15811 - ill check this PR over in the meantime as its pretty annoying atm

[justincely]

@phlax thanks! I didn't realize someone else was working on anything similar, so just let me know if i'm on the wrong track or if this is superfluous considering yours. Just seemed low hanging fruit

[phlax]

lgtm - it does the same thing as now in terms of pushing but is more likely to provide info on how to resolve and not python stacktrace

thanks @justincely

[phlax]

/retest

[repokitteh-read-only]

Retrying Azure Pipelines:
Retried failed jobs in: envoy-presubmit

🐱

Caused by: a #16505 (comment) was created by @phlax.

see: more, trace.