Fix layout saving error
Fix layout saving error

As a result of commit b49226e085 FileAccess::open no longer returns ERR_CANT_OPEN if the file cannot be found/opened.
Instead check against ERR_FILE_NOT_FOUND or ERR_FILE_CANT_OPEN.

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