Update condition before calling normalizeCodeOwner

Update the condition in the ternary operator in the resolveCodeOwner
function to check that match.owners isn't empty before calling
normalizeCodeOwner with match.owners[0]

Before this change normalizeCodeOwner could potentially throw an
error during processing if the `match` object exists but the
match.owners array is empty because normalizeCodeOwner will be passed
`undefined` instead of the string it expects.

Signed-off-by: Isabel Tomb <isabelgtomb@gmail.com>

.changeset/twenty-laws-tie.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-catalog-backend': patch
+---
+
+Updated condition in resolveCodeOwner to fix a bug where normalizeCodeOwner could potentially be called with an invalid arg causing an error in CodeOwnersProcessor.

plugins/catalog-backend/src/processors/codeowners/resolve.ts

@@ -30,7 +30,9 @@ export function resolveCodeOwner(
   const { filepath } = parseGitUrl(catalogInfoFileUrl);
   const match = codeowners.matchFile(filepath, codeOwnerEntries);
 
-  return match ? normalizeCodeOwner(match.owners[0]) : undefined;
+  return match?.owners?.length
+    ? normalizeCodeOwner(match.owners[0])
+    : undefined;
 }
 
 export function normalizeCodeOwner(owner: string) {