refactor: apply review suggestions

Signed-off-by: Camila Belo <camilaibs@gmail.com>

plugins/search-backend-node/src/engines/LunrSearchEngine.test.ts

@@ -959,7 +959,7 @@ describe('LunrSearchEngine', () => {
             filters: {},
           }),
       ).rejects.toThrow(
-        'Missing index for unknown. This means there are no documents to search through',
+        "Missing index for unknown. This could be because the index hasn't been created yet or there was a problem during index creation.",
       );
     });
   });

plugins/search-backend-node/src/engines/LunrSearchEngine.ts

@@ -170,7 +170,7 @@ export class LunrSearchEngine implements SearchEngine {
 
     if (documentTypes?.length && !indexKeys.length) {
       throw new MissingIndexError(
-        `Missing index for ${documentTypes?.toString()}. This means there are no documents to search through.`,
+        `Missing index for ${documentTypes?.toString()}. This could be because the index hasn't been created yet or there was a problem during index creation.`,
       );
     }