There are a number of instances where OSL_ASSERT are just not
necessary. Also, we need to change from testing if something
is/is not equal to nullptr and just use the simpler form.

Change-Id: I7e0b7deb12f0189030f66dd14ab23287341c82b7
Reviewed-on: https://gerrit.libreoffice.org/38507Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Chris Sherlock <chris.sherlock79@gmail.com>