[UWP] [Export] added additional checks for blank values
[UWP] [Export] added additional checks for blank values

`Short Name` and `Publisher Display Name` are mandatory.
You can't even sign the app package without them in the manifest.

Valentactive/godot,Faless/godot,MarianoGnu/godot,vkbsb/godot,pkowal1982/godot,vkbsb/godot,godotengine/godot,Zylann/godot,akien-mga/godot,BastiaanOlij/godot,ZuBsPaCe/godot,josempans/godot,DmitriySalnikov/godot,BastiaanOlij/godot,ZuBsPaCe/godot,josempans/godot,BastiaanOlij/godot,pkowal1982/godot,Paulloz/godot,godotengine/godot,Valentactive/godot,MarianoGnu/godot,pkowal1982/godot,vkbsb/godot,sanikoyes/godot,guilhermefelipecgs/godot,pkowal1982/godot,BastiaanOlij/godot,godotengine/godot,DmitriySalnikov/godot,firefly2442/godot,vnen/godot,akien-mga/godot,ZuBsPaCe/godot,BastiaanOlij/godot,pkowal1982/godot,Zylann/godot,Faless/godot,firefly2442/godot,DmitriySalnikov/godot,akien-mga/godot,guilhermefelipecgs/godot,akien-mga/godot,Shockblast/godot,sanikoyes/godot,josempans/godot,Faless/godot,Paulloz/godot,MarianoGnu/godot,pkowal1982/godot,MarianoGnu/godot,Valentactive/godot,Paulloz/godot,guilhermefelipecgs/godot,vkbsb/godot,BastiaanOlij/godot,vnen/godot,pkowal1982/godot,MarianoGnu/godot,vnen/godot,vkbsb/godot,vkbsb/godot,ex/godot,Faless/godot,honix/godot,sanikoyes/godot,josempans/godot,vkbsb/godot,Faless/godot,josempans/godot,vnen/godot,Zylann/godot,BastiaanOlij/godot,ex/godot,Paulloz/godot,ex/godot,Faless/godot,Zylann/godot,godotengine/godot,josempans/godot,Shockblast/godot,Shockblast/godot,ZuBsPaCe/godot,Valentactive/godot,honix/godot,honix/godot,Shockblast/godot,josempans/godot,ZuBsPaCe/godot,sanikoyes/godot,guilhermefelipecgs/godot,akien-mga/godot,Faless/godot,honix/godot,honix/godot,Zylann/godot,akien-mga/godot,MarianoGnu/godot,DmitriySalnikov/godot,ex/godot,akien-mga/godot,sanikoyes/godot,Paulloz/godot,firefly2442/godot,ex/godot,sanikoyes/godot,sanikoyes/godot,DmitriySalnikov/godot,Valentactive/godot,vnen/godot,guilhermefelipecgs/godot,Zylann/godot,godotengine/godot,MarianoGnu/godot,Zylann/godot,firefly2442/godot,godotengine/godot,guilhermefelipecgs/godot,ZuBsPaCe/godot,guilhermefelipecgs/godot,firefly2442/godot,vkbsb/godot,DmitriySalnikov/godot,Shockblast/godot,firefly2442/godot,akien-mga/godot,pkowal1982/godot,Shockblast/godot,MarianoGnu/godot,ZuBsPaCe/godot,josempans/godot,Zylann/godot,ex/godot,godotengine/godot,godotengine/godot,vnen/godot,BastiaanOlij/godot,ex/godot,Paulloz/godot,Shockblast/godot,guilhermefelipecgs/godot,DmitriySalnikov/godot,vnen/godot,Valentactive/godot,Faless/godot,Shockblast/godot,Valentactive/godot,firefly2442/godot,honix/godot,firefly2442/godot,ZuBsPaCe/godot,Paulloz/godot,sanikoyes/godot,vnen/godot,ex/godot,Valentactive/godot