Allow null Files to be passed to TextFile again.
Allow null Files to be passed to TextFile again.

We do this for temporary configuration files which are never saved
(e.g. the addon settings). It's a bit of a kludge, but for now we
should maintain it.

Change-Id: I656b924221eded5bbd98dfa4c276ab6d43b682e0
Fixes-Issue: CLIENT-510
Reviewed-on: http://gerrit.dmdirc.com/3507
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <79e2475f81a6317276bf7cbb3958b20d289b78df@dmdirc.com>

DMDirc/Util