fix: image was sent to an unsupported LLM when sending second message (…

…langgenius#3268)

api/core/workflow/nodes/llm/llm_node.py

@@ -10,7 +10,7 @@
 from core.memory.token_buffer_memory import TokenBufferMemory
 from core.model_manager import ModelInstance, ModelManager
 from core.model_runtime.entities.llm_entities import LLMUsage
-from core.model_runtime.entities.message_entities import PromptMessage
+from core.model_runtime.entities.message_entities import PromptMessage, PromptMessageContentType
 from core.model_runtime.entities.model_entities import ModelType
 from core.model_runtime.model_providers.__base.large_language_model import LargeLanguageModel
 from core.model_runtime.utils.encoders import jsonable_encoder
@@ -434,6 +434,22 @@ def _fetch_prompt_messages(self, node_data: LLMNodeData,
         )
         stop = model_config.stop
 
+        vision_enabled = node_data.vision.enabled
+        for prompt_message in prompt_messages:
+            if not isinstance(prompt_message.content, str):
+                prompt_message_content = []
+                for content_item in prompt_message.content:
+                    if vision_enabled and content_item.type == PromptMessageContentType.IMAGE:
+                        prompt_message_content.append(content_item)
+                    elif content_item.type == PromptMessageContentType.TEXT:
+                        prompt_message_content.append(content_item)
+
+                if len(prompt_message_content) > 1:
+                    prompt_message.content = prompt_message_content
+                elif (len(prompt_message_content) == 1
+                      and prompt_message_content[0].type == PromptMessageContentType.TEXT):
+                    prompt_message.content = prompt_message_content[0].data
+
         return prompt_messages, stop
 
     @classmethod