1.7.7

[Added] Support for Craft 2.6.2951.
[Improved] Now restores original nav if errors are thrown during the nav generation process (PHP7+ only).
[Improved] Enforce only image selection for custom icon.
[Improved] Allow custom icons to override default Craft/Plugin icons.
[Fixed] Fixed selected custom icon not populating asset element select field.
[Fixed] Check if a custom icon asset exists before trying to apply it to the nav.