gh processor passes over repos without default branch

Signed-off-by: Brian Fletcher <brian@roadie.io>

.changeset/cuddly-impalas-wave.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-catalog-backend': patch
+---
+
+GitHub discovery processor passes over repositories that do not have a default branch

plugins/catalog-backend/src/ingestion/processors/GithubDiscoveryProcessor.ts

@@ -108,9 +108,15 @@ export class GithubDiscoveryProcessor implements CatalogProcessor {
     );
 
     for (const repository of matching) {
-      const path = `/blob/${
-        branch === '-' ? repository.defaultBranchRef.name : branch
-      }${catalogPath}`;
+      const branchName = branch === '-' ? repository.defaultBranchRef?.name : branch;
+      
+      if (!branchName) {
+        this.logger.info(`the repository ${repository.url} does not have a default branch, skipping`);
+        continue;
+      }
+      
+      const path = `/blob/${branchName}${catalogPath}`;
+      
       emit(
         results.location(
           {