security/keepassx: Unbreak with Clang 6
lib/AutoTypeX11.cpp:195:16: error: assigning to 'Window' (aka 'unsigned long') from incompatible type 'nullptr_t'
focusWindow = NULL; ^~~~
http://beefy12.nyi.freebsd.org/data/head-amd64-default/p475044_s336572/logs/KeePassX-0.4.4.log