fix: Resolve nonlocal variable error in directory selection

src/streamlit_app.py

@@ -213,8 +213,16 @@ with col1:
                         root = tk.Tk()
                         root.withdraw()
                         root.wm_attributes('-topmost', 1)
+                        root.after(10)  # Add a small delay
+                        # Create and run the main loop in a way that doesn't block
+                        path_holder = []
+                        def select_dir():
                             path = filedialog.askdirectory(title="Select Source Directory")
-                        if path:
+                            path_holder.append(path)
+                            root.quit()
+                        root.after(20, select_dir)
+                        root.mainloop()
+                        if path_holder and path_holder[0]:
                             st.session_state['source_dir_selected'] = path
                             st.rerun()
                         root.destroy()
@@ -262,8 +270,16 @@ with col1:
                         root = tk.Tk()
                         root.withdraw()
                         root.wm_attributes('-topmost', 1)
+                        root.after(10)  # Add a small delay
+                        # Create and run the main loop in a way that doesn't block
+                        path_holder = []
+                        def select_dir():
                             path = filedialog.askdirectory(title="Select Destination Directory")
-                        if path:
+                            path_holder.append(path)
+                            root.quit()
+                        root.after(20, select_dir)
+                        root.mainloop()
+                        if path_holder and path_holder[0]:
                             st.session_state['dest_dir_selected'] = path
                             st.rerun()
                         root.destroy()