devel/qdevelop: Fix build with Clang 6

src/mainimpl.cpp:82:19: error: cannot initialize a parameter of type 'QStatusBar *' with an rvalue of type 'bool'

setStatusBar( false );
              ^~~~~

http://beefy12.nyi.freebsd.org/data/head-amd64-default/p475044_s336572/logs/qdevelop-0.28_3.log