don't check for serial in isr if prompting for input

cubesatsim/cubesatsim.ino

@@ -3609,6 +3609,8 @@ void load_files() {
 
 void serial_input() {
 	
+  if (!prompt) {  // only query if not in the middle of prompting
+	  
   if (Serial.available() > 0) {  // check for user input on serial port
  
 //    blink(50);
@@ -3708,6 +3710,7 @@ void serial_input() {
     sleep(2.0);		    
    }
  }
+ }
 }
 
 void prompt_for_input() {