glx/apple: Fixed glx context memory leak in case of failure.

Reviewed-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Jeremy Huddleston Sequoia: <jeremyhu@apple.com>

src/glx/apple/apple_glx_context.c

@@ -142,6 +142,7 @@ apple_glx_create_context(void **ptr, Display * dpy, int screen,
    if (sharedac && !is_context_valid(sharedac)) {
       *errorptr = GLXBadContext;
       *x11errorptr = false;
+      free(ac);
       return true;
    }