No empty metadata (#6713)

Author: jdolle

.changeset/green-boats-begin.md

@@ -0,0 +1,5 @@
+---
+'hive': patch
+---
+
+Do not store empty metadata in db

packages/services/schema/src/lib/metadata-extraction.ts

@@ -62,7 +62,7 @@ export const extractMetadata = (documentAst: DocumentNode, source: string): Subg
           },
           [] as Array<{ name: string; content: string; source: string }>,
         );
-      if (metadata) {
+      if (metadata?.length) {
         schemaCoordinateMetadataMappings.set(schemaCoordinate, metadata);
       }
     }