Added a check to ensure the input text is a string before proceeding with parsing (#22809)

Co-authored-by: -LAN- <laipz8200@outlook.com>

api/core/model_runtime/entities/message_entities.py

@@ -156,6 +156,23 @@ class PromptMessage(ABC, BaseModel):
         """
         return not self.content
 
+    def get_text_content(self) -> str:
+        """
+        Get text content from prompt message.
+
+        :return: Text content as string, empty string if no text content
+        """
+        if isinstance(self.content, str):
+            return self.content
+        elif isinstance(self.content, list):
+            text_parts = []
+            for item in self.content:
+                if isinstance(item, TextPromptMessageContent):
+                    text_parts.append(item.data)
+            return "".join(text_parts)
+        else:
+            return ""
+
     @field_validator("content", mode="before")
     @classmethod
     def validate_content(cls, v):