[gnome-2048] Fix crash with fast gestures.

[Arnaud B. <arnaudb src gnome org>]

commit c7884d1ae6ed90f07014da753aba35373063ea03
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Thu Jan 31 17:17:18 2019 +0100

    Fix crash with fast gestures.
    
    Add the same guard than with keys.

 src/application.vala | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/src/application.vala b/src/application.vala
index 83408d0..b8777cf 100644
--- a/src/application.vala
+++ b/src/application.vala
@@ -675,6 +675,9 @@ private class Application : Gtk.Application
 
     private inline void _on_swipe (GestureSwipe gesture, double velocity_x, double velocity_y)
     {
+        if (_game.cannot_move ())
+            return;
+
         double abs_x = velocity_x.abs ();
         double abs_y = velocity_y.abs ();
         if (abs_x * abs_x + abs_y * abs_y < 400.0)