warnings building latest tgui

Some warnings appeared building (32bit) latest tgui source code (github) with visual studio 2015.

nanosvg.h(807): warning C4702: unreachable code
GuiBuilder.cpp(1480): warning C4800: 'unsigned int': forcing value to bool 'true' or 'false' (performance warning)
GuiBuilder.cpp(1481): warning C4800: 'unsigned int': forcing value to bool 'true' or 'false' (performance warning)
GuiBuilder.cpp(1482): warning C4800: 'unsigned int': forcing value to bool 'true' or 'false' (performance warning)

Thanks, the warnings have been fixed.

The unreachable code warning also shows up in my AppVeyor builds, the others don't.
There still seems to be a signed/unsigned mismatch warning that I get in my VS2017 build that isn't showing up with VS2015, but I'll fix that later (as my VS2017 build is a unity build which makes it harder to find where the warning came from).