fix: Don't attempt out of bounds buffer replacments

Author: Muscraft

src/renderer/styled_buffer.rs

@@ -103,6 +103,11 @@ impl StyledBuffer {
         if start == end {
             return;
         }
+        // If the replacement range would be out of bounds, do nothing, as we
+        // can't replace things that don't exist.
+        if start > self.lines[line].len() || end > self.lines[line].len() {
+            return;
+        }
         let _ = self.lines[line].drain(start..(end - string.chars().count()));
         for (i, c) in string.chars().enumerate() {
             self.lines[line][start + i] = StyledChar::new(c, ElementStyle::LineNumber);

tests/rustc_tests.rs

@@ -2891,7 +2891,6 @@ $DIR/short-error-format.rs:8:7: error[E0599]: no method named `salut` found for
 }
 
 #[test]
-#[should_panic(expected = "range end index 47 out of range for slice of length 26")]
 fn rustdoc_ui_diagnostic_width() {
     // tests/rustdoc-ui/diagnostic-width.rs