Bug 427243 - NPE in AutoDetectLibraryFolderJob.getFoldersFromNames()

Simple null check avoids the problem.

Bug: 427243
Change-Id: Ibc46d243ba62f3c14c95c58a4a9ad59f31edebb7
Signed-off-by: Kaloyan Raev <kaloyan.r@zend.com>