evas: fix dereference after null check

Summary:
Static analysis tool reports passing a null pointer 'im->gc' to
_evas_gl_image_cache_add which directly dereferences it, so lets
be sure that 'im->gc' is valid before passing it to cache_add

Reviewers: Hermet, jsuya, herb, zmike

Reviewed By: zmike

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D11676

src/modules/evas/engines/gl_common/evas_gl_image.c

@@ -716,7 +716,7 @@ evas_gl_common_image_free(Evas_GL_Image *im)
      {
         if (!im->cs.no_free) free(im->cs.data);
      }
-   if (im->cached)
+   if (im->cached && im->gc)
      {
         if (_evas_gl_image_cache_add(im)) return;
      }