Only allow firing missiles in missile mode (#5)

src/components/TopLevel.component.js

@@ -170,6 +170,7 @@ export default class TopLevelComponent extends Component {
      * @param {number} column_index
      */
     on_missile_fired([row_index, column_index]) {
+        if ( this.player_is_firing_missiles ) {
             game_service.attempt_missile_fire([row_index, column_index])
 
             // Give the user time to see whether they hit or not
@@ -177,6 +178,7 @@ export default class TopLevelComponent extends Component {
                 game_service.advance_game_state()
             }, 5000)
         }
+    }
 
     /**
      * Called when the player has confirmed the player change.