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);
@@ -3709,6 +3711,7 @@ void serial_input() {
    }
  }
  }
+}
 
 void prompt_for_input() {