va: fix handling when all wayland backends fail

when all backend failed vaGetDisplayWl will just return a context that
was already destroyed. This leads to crashes if downstream tries to use
the context.

va/wayland/va_wayland.c

@@ -133,12 +133,10 @@ vaGetDisplayWl(struct wl_display *display)
 
     for (i = 0; g_backends[i].create != NULL; i++) {
         if (g_backends[i].create(pDisplayContext))
-            break;
+            return (VADisplay)pDisplayContext;
         g_backends[i].destroy(pDisplayContext);
     }
 
-    return (VADisplay)pDisplayContext;
-
 error:
     va_DisplayContextDestroy(pDisplayContext);
     return NULL;