refac: memory handling

backend/open_webui/routers/memories.py

@@ -82,6 +82,10 @@ class QueryMemoryForm(BaseModel):
 async def query_memory(
     request: Request, form_data: QueryMemoryForm, user=Depends(get_verified_user)
 ):
+    memories = Memories.get_memories_by_user_id(user.id)
+    if not memories:
+        raise HTTPException(status_code=404, detail="No memories found for user")
+
     results = VECTOR_DB_CLIENT.search(
         collection_name=f"user-memory-{user.id}",
         vectors=[request.app.state.EMBEDDING_FUNCTION(form_data.content, user=user)],