Fix crash with filtered diagnostics in gutter (e.g. when diagnostics aren't visible)

helix-view/src/gutter.rs

@@ -83,10 +83,8 @@ pub fn diagnostic<'doc>(
 
                 let diagnostics_on_line = after.chain(before);
 
-                // This unwrap is safe because the iterator cannot be empty as it contains at least the item found by the binary search.
-                let diagnostic = diagnostics_on_line.max_by_key(|d| d.severity).unwrap();
-
-                write!(out, "●").unwrap();
+                if let Some(diagnostic) = diagnostics_on_line.max_by_key(|d| d.severity) {
+                    write!(out, "●").ok();
                     return Some(match diagnostic.severity {
                         Some(Severity::Error) => error,
                         Some(Severity::Warning) | None => warning,
@@ -94,6 +92,7 @@ pub fn diagnostic<'doc>(
                         Some(Severity::Hint) => hint,
                     });
                 }
+            }
             None
         },
     )