Fix jshint warnings in VipsScaler
completed by: ☃ unicodesnowman
mentors: Gergő Tisza
VipsScaler is an image handler optimized for low memory consumption with huge images. Its Javascript code currently fails the jshint coding guideline tests which are the standard for MediaWiki software; the task is to fix that.
This is T63643 in Wikimedia's issue tracker.
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