Button : Fix lingering hover regression
Button : Fix lingering hover regression

47239f7 introduced a regression with lingering hover highlights.

hradec/gaffer,GafferHQ/gaffer,ImageEngine/gaffer,boberfly/gaffer,hradec/gaffer,hradec/gaffer,johnhaddon/gaffer,johnhaddon/gaffer,boberfly/gaffer,johnhaddon/gaffer,GafferHQ/gaffer,andrewkaufman/gaffer,boberfly/gaffer,ImageEngine/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,GafferHQ/gaffer,boberfly/gaffer,GafferHQ/gaffer,hradec/gaffer,andrewkaufman/gaffer,andrewkaufman/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,hradec/gaffer,ImageEngine/gaffer,johnhaddon/gaffer,andrewkaufman/gaffer