Fix undefined behavior by calling on almost destroyed object

Because mView is in the process of being destroyed we shouldn't try to touch it too much.

Warning from ubsan:
    runtime error: member call on address 0x606000118e80 which does not
    point to an object of type 'QAbstractScrollArea'

Reviewed By: ngraham

Differential Revision: https://phabricator.kde.org/D28342