Fix safegaurd against mono or already surround files

app.py

@@ -259,8 +259,9 @@ def smart_mode_process(input_file, api_key, multi_singer=False):
     os.unlink(wav)
     p((0, 8), "Loading File")
 
-    if data.ndim != 2:
-        raise gr.Error("Expected stereo input")
+    if data.ndim != 2 or data.shape[1] != 2:
+        raise gr.Error("Expected stereo input (2 channels), got something else.")
+
     L, R = data[:, 0], data[:, 1]
 
     # Step 1: LFE from lowpass