[INTERNAL] fixed NPEs in SWTUtils

Used the wrong logger for logging statements that lead to NPE because
the used logger can be null.

Change-Id: I85862e7bb7cea946ff7fb65c00e69f674a5551a3
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1322
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>