Ref T12855. PHP7 introduced "Throwables", which are sort of like super exceptions. Some errors that PHP raises at runtime have become Throwables instead of old-school errors now.
The major effect this has is blank pages during development under PHP7 for certain classes of errors: they skip all the nice "show a pretty error" handlers and
This isn't a compelete fix, but catches the most common classes of unexpected Throwable and sends them through the normal machinery. Principally, it shows a nice stack trace again instead of a blank page for a larger class of typos and minor mistakes.
