fixed a bug preventing from sim run

main.py

@@ -655,8 +655,10 @@ def check_tun_interface(ipv6_addr):
         return fnd1 and fnd2
 
     def start_sim():
+        if builder.node_list_index < 1:
+            return
         tunip = sim_settings['varTunip']
-        if not (check_tun_interface(tunip)):
+        if not (check_tun_interface(tunip)) and not sim_settings['varTundev'].get():
             print("Tunnel interface not found")
             tk.messagebox.showwarning(title="Tun not found", message="Tunnel interface not found with IP: " + tunip)
             return
@@ -727,7 +729,7 @@ def open_plot_dialog():
     status = tk.Label(status_frame, text="Ready", anchor=tk.W, bg="grey98")
     status.pack(padx=10, pady=0, side=tk.LEFT)
     # Version 0.MONTH+ABCDE...
-    version = tk.Label(status_frame, text="Version: " + "0.4b", anchor=tk.E, bg="grey98")
+    version = tk.Label(status_frame, text="Version: " + "0.4c", anchor=tk.E, bg="grey98")
     version.pack(padx=10, pady=0, side=tk.RIGHT)
 
     # Create the labelframe