Fix missing except block in preprocessing try/except

app.py

@@ -952,6 +952,9 @@ with main_tab1:
                     # Remove trailing comma and space
                     meta_text = meta_text.rstrip(", ")
                     st.caption(meta_text)
+                except Exception as e:
+                    st.error(f"Error in preprocessing: {str(e)}")
+                    st.info("Try using grayscale preprocessing for PNG images with transparency")
             
             # Empty container for progress indicators - will be filled during processing
             progress_placeholder = st.empty()