feat: better error handling

backend/constants.py

@@ -60,3 +60,5 @@ class ERROR_MESSAGES(str, Enum):
     MODEL_NOT_FOUND = lambda name="": f"Model '{name}' was not found"
     OPENAI_NOT_FOUND = lambda name="": f"OpenAI API was not found"
     OLLAMA_NOT_FOUND = "WebUI could not connect to Ollama"
+
+    EMPTY_CONTENT = "The content provided is empty. Please ensure that there is text or data present before proceeding."