Fix EXIF stripping via message compose input button
Fix EXIF stripping via message compose input button

It looks like previously we were stripping EXIF data when images were
dragged and dropped into the composer or pasted, but unfortunately this
default wasn't set for the input button itself. This resolves the issue
so that when an input button is created it defaults to `{ stripExif =
true }`.

ssbc/patchwork,ssbc/patchwork