Fix: refine error msg. (#11380)

### Type of change

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

api/apps/kb_app.py

@@ -886,6 +886,7 @@ async def check_embedding():
 
         try:
             v, _ = emb_mdl.encode([title, txt_in])
+            assert len(v[1]) == len(ck["vector"]), f"The dimension ({len(v[1])}) of given embedding model is different from the original ({len(ck['vector'])})"
             sim_content = _cos_sim(v[1], ck["vector"])
             title_w = 0.1
             qv_mix = title_w * v[0] + (1 - title_w) * v[1]
@@ -895,8 +896,8 @@ async def check_embedding():
             if sim_mix > sim:
                 sim = sim_mix
                 mode = "title+content"
-        except Exception:
-            return get_error_data_result(message="embedding failure")
+        except Exception as e:
+            return get_error_data_result(message=f"Embedding failure. {e}")
 
         eff_sims.append(sim)
         results.append({