cocoa: Fix assert to use SDL_assert
diff --git a/src/video/cocoa/SDL_cocoametalview.m b/src/video/cocoa/SDL_cocoametalview.m
index 4255d0d..3d7e147 100644
--- a/src/video/cocoa/SDL_cocoametalview.m
+++ b/src/video/cocoa/SDL_cocoametalview.m
@@ -121,7 +121,7 @@
     SDL_cocoametalview* metalview = [view viewWithTag:METALVIEW_TAG];
     if (metalview) {
         CAMetalLayer *layer = (CAMetalLayer*)metalview.layer;
-        assert(layer != NULL);
+        SDL_assert(layer != NULL);
         if (w) {
             *w = layer.drawableSize.width;
         }