fix(plugins/catalog-backend-module-unprocessed): correctly translate owner to string in case of nullish value

Signed-off-by: secustor <sebastian@poxhofer.at>

.changeset/cyan-suns-shave.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-catalog-backend-module-unprocessed': patch
+---
+
+Correctly convert owner to string in case owner has not been provided

plugins/catalog-backend-module-unprocessed/src/UnprocessedEntitiesModule.ts

@@ -162,7 +162,7 @@ export class UnprocessedEntitiesModule {
         return res.json(
           await this.unprocessed({
             reason: 'failed',
-            owner: String(req.query.owner),
+            owner: req.query.owner?.toString(),
           }),
         );
       })
@@ -170,7 +170,7 @@ export class UnprocessedEntitiesModule {
         return res.json(
           await this.unprocessed({
             reason: 'pending',
-            owner: String(req.query.owner),
+            owner: req.query.owner?.toString(),
           }),
         );
       })