Show confirmation dialog when attempting to close while a game is loaded (#1582)

Ryujinx/Ui/MainWindow.cs

@@ -917,14 +917,24 @@ namespace Ryujinx.Ui
         }
 
         private void Exit_Pressed(object sender, EventArgs args)
+        {
+            if (!_gameLoaded || GtkDialog.CreateExitDialog())
             {
                 End(_emulationContext);
             }
+        }
 
         private void Window_Close(object sender, DeleteEventArgs args)
+        {
+            if (!_gameLoaded || GtkDialog.CreateExitDialog())
             {
                 End(_emulationContext);
             }
+            else
+            {
+                args.RetVal = true;
+            }
+        }
 
         private void StopEmulation_Pressed(object sender, EventArgs args)
         {