Sebastian Holtermann authored Nov 27, 2018 and Brad King committed Nov 27, 2018

In CMake 3.13.0 when a target has ``AUTOUIC`` enabled but doesn't
link against Qt5Widgets, the uic executable string is empty and
an error string "The uic executable \"\" does not exist" is generated.
In CMake 3.12 ``AUTOUIC`` was silently disabled instead.
This patch fixes the regression and restores the behavior of CMake 3.12.

Fixes: #18630