So the auto-spell-checking is hyper-optimized to add the words to the
auto-complete list as well, and call SetAutoCompleteWordDirty().

But if you disable the auto-spell-checking, then a separate function
SwTextFrm::CollectAutoCmplWrds() will be called, which is buggy because
it only resets the dirty flag if at least one word of sufficient length
was found in the paragraph, which is never the case for an empty
paragraph.

Change-Id: Idec64fc3c379301426a44e06a1114c474de36014
(cherry picked from commit 97c6dac6)
Reviewed-on: https://gerrit.libreoffice.org/18589Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>