If the root item of the dir model is deleted, but it is not the first
item in the list that KDirModelPrivate::_k_slotDeleteItems(...) gets
from the dir lister, a crash may result because
KDirModelPrivate::removeFromNodeHash(...) calls isDir() for a null
KFileItem. This commit extends the protection agains this kind of crash
that has been introduced in c8939409 for
the first item to the rest of the list.
BUG: 196695
FIXED-IN: 4.6.4
(cherry picked from commit 83538b43)