eet: handle decode failures as errors in variant decoding

Summary:
all other null returns of _eet_data_descriptor_decode() are treated as
fatal errors when decoding, and failure to do so in this case guarantees
errors later due to incomplete decoding

@fix

ref T5379
Depends on D6293

Reviewers: devilhorns, ManMower

Reviewed By: ManMower

Subscribers: cedric, #committers

Tags: #efl

Maniphest Tasks: T5379

Differential Revision: https://phab.enlightenment.org/D6294

src/lib/eet/eet_data.c

@@ -4505,8 +4505,7 @@ eet_data_get_variant(Eet_Free_Context     *context,
                                                       echnk->data,
                                                       echnk->size,
                                                       NULL, 0);
-               if (!data_ret)
-                 break;
+               EINA_SAFETY_ON_TRUE_GOTO(!data_ret, on_error);
 
                /* And point to the variant data. */
                *(void **)data = data_ret;