Fix：The OpenAI-Compatible Agent API returns an incorrect message (#8177)

### What problem does this PR solve?

https://github.com/infiniflow/ragflow/issues/8175

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

agent/canvas.py

@@ -169,6 +169,7 @@ class Canvas:
     def run(self, running_hint_text = "is running...🕞", **kwargs):
         if not running_hint_text or not isinstance(running_hint_text, str):
             running_hint_text = "is running...🕞"
+        bypass_begin = bool(kwargs.get("bypass_begin", False))
 
         if self.answer:
             cpn_id = self.answer[0]
@@ -188,6 +189,12 @@ class Canvas:
         if not self.path:
             self.components["begin"]["obj"].run(self.history, **kwargs)
             self.path.append(["begin"])
+            if bypass_begin:
+                cpn = self.get_component("begin")
+                downstream = cpn["downstream"]
+                self.path.append(downstream)
+
+
 
         self.path.append([])
 

agent/component/answer.py

@@ -64,14 +64,17 @@ class Answer(ComponentBase, ABC):
             for ii, row in stream.iterrows():
                 answer += row.to_dict()["content"]
                 yield {"content": answer}
-        else:
+        elif stream is not None:
             for st in stream():
                 res = st
                 yield st
-        if self._param.post_answers:
+        if self._param.post_answers and res:
             res["content"] += random.choice(self._param.post_answers)
             yield res
 
+        if res is None:
+            res = {"content": ""}
+
         self.set_output(res)
 
     def set_exception(self, e):

agent/component/base.py

@@ -442,7 +442,6 @@ class ComponentBase(ABC):
             elif q.get("value"):
                 outs.append(pd.DataFrame([{"content": q["value"]}]))
         return outs
-
     def get_input(self):
         if self._param.debug_inputs:
             return pd.DataFrame([{"content": v["value"]} for v in self._param.debug_inputs if v.get("value")])