Fix session API issues. (#3939)

### What problem does this PR solve?


### Type of change

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

api/apps/sdk/session.py

@@ -374,14 +374,14 @@ def chatbot_completions(dialog_id):
         req["quote"] = False
 
     if req.get("stream", True):
-        resp = Response(iframe_completion(objs[0].tenant_id, dialog_id, **req), mimetype="text/event-stream")
+        resp = Response(iframe_completion(dialog_id, **req), mimetype="text/event-stream")
         resp.headers.add_header("Cache-control", "no-cache")
         resp.headers.add_header("Connection", "keep-alive")
         resp.headers.add_header("X-Accel-Buffering", "no")
         resp.headers.add_header("Content-Type", "text/event-stream; charset=utf-8")
         return resp
 
-    for answer in agent_completion(objs[0].tenant_id, dialog_id, **req):
+    for answer in iframe_completion(dialog_id, **req):
         return get_result(data=answer)
 
 

api/db/services/canvas_service.py

@@ -89,6 +89,8 @@ def completion(tenant_id, agent_id, question, session_id=None, stream=True, **kw
         assert e, "Session not found!"
         canvas = Canvas(json.dumps(conv.dsl), tenant_id)
 
+    if not conv.message:
+        conv.message = []
     messages = conv.message
     question = {
         "role": "user",

api/db/services/conversation_service.py

@@ -176,6 +176,8 @@ def iframe_completion(dialog_id, question, session_id=None, stream=True, **kwarg
         e, conv = API4ConversationService.get_by_id(session_id)
         assert e, "Session not found!"
 
+    if not conv.message:
+        conv.message = []
     messages = conv.message
     question = {
         "role": "user",