edje_cc: fix crash on image data initialization
Summary:
Since commit
a8538bacce1457a91e28b39a6417eaadb4744b50 a crash occurs when
Images.Set.Image is unused.
To avoid a crash, this patch skips setting image data for unused image sets.
Test Plan:
$edje_cc basic.edc
basic.edc
```
collections {
set {
name: "bubble";
image {
image: "bubble.png" COMP;
}
}
}
```
Reviewers: raster
Subscribers: cedric, #reviewers, #committers, eagleeye
Tags: #efl
Differential Revision: https://phab.enlightenment.org/D12063
Change-Id: Ibcb14df831f0a6eb51d69267b379f6480256969f