[gtk+] Quiet a compiler warning

[Matthias Clasen <matthiasc src gnome org>]

commit 76461a8004caf4490f84140b0551d1f5296241f6
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Jan 10 07:35:46 2018 -0500

    Quiet a compiler warning
    
    Avoid this warning the other way, without bumping the libvulkan
    dependency.

 gdk/gdkvulkancontext.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gdk/gdkvulkancontext.c b/gdk/gdkvulkancontext.c
index 8bfbd80..1c4e790 100644
--- a/gdk/gdkvulkancontext.c
+++ b/gdk/gdkvulkancontext.c
@@ -93,7 +93,7 @@ G_DEFINE_ABSTRACT_TYPE_WITH_CODE (GdkVulkanContext, gdk_vulkan_context, GDK_TYPE
 const char *
 gdk_vulkan_strerror (VkResult result)
 {
-  switch (result)
+  switch ((int)result)
   {
     case VK_SUCCESS:
       return "Command successfully completed.";