Replace OSL_VERIFY with if-statement and SAL_WARN.

Change-Id: Ib286a2151fe19a91b4e9db8db9f92ac0d5264d36
Reviewed-on: https://gerrit.libreoffice.org/72330
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>