eina_abstract_content: Fix resource leak

If we error out in this function, then we should be freeing 'content'
also as it was previously calloc'd above

Fixes CID1420317

src/lib/eina/eina_abstract_content.c

@@ -142,6 +142,7 @@ eina_content_new(Eina_Slice data, const char *type)
 err:
    free(content->data.mem);
    content->data.mem = NULL;
+   free(content);
    return NULL;
 }