Fix crash when pressing up on an empty `PopupMenu`
Fix crash when pressing up on an empty `PopupMenu`

firefly2442/godot,Shockblast/godot,Zylann/godot,pkowal1982/godot,vkbsb/godot,josempans/godot,BastiaanOlij/godot,firefly2442/godot,ZuBsPaCe/godot,sanikoyes/godot,pkowal1982/godot,ZuBsPaCe/godot,Zylann/godot,Zylann/godot,vkbsb/godot,Shockblast/godot,guilhermefelipecgs/godot,Zylann/godot,firefly2442/godot,guilhermefelipecgs/godot,godotengine/godot,BastiaanOlij/godot,godotengine/godot,vkbsb/godot,BastiaanOlij/godot,josempans/godot,josempans/godot,pkowal1982/godot,BastiaanOlij/godot,godotengine/godot,guilhermefelipecgs/godot,Shockblast/godot,Shockblast/godot,Shockblast/godot,vkbsb/godot,firefly2442/godot,BastiaanOlij/godot,vkbsb/godot,firefly2442/godot,Shockblast/godot,vkbsb/godot,BastiaanOlij/godot,ZuBsPaCe/godot,godotengine/godot,pkowal1982/godot,firefly2442/godot,firefly2442/godot,ZuBsPaCe/godot,sanikoyes/godot,sanikoyes/godot,guilhermefelipecgs/godot,Zylann/godot,sanikoyes/godot,ZuBsPaCe/godot,sanikoyes/godot,godotengine/godot,Zylann/godot,Shockblast/godot,pkowal1982/godot,Zylann/godot,josempans/godot,Zylann/godot,josempans/godot,guilhermefelipecgs/godot,ZuBsPaCe/godot,sanikoyes/godot,josempans/godot,Shockblast/godot,BastiaanOlij/godot,josempans/godot,pkowal1982/godot,pkowal1982/godot,vkbsb/godot,sanikoyes/godot,ZuBsPaCe/godot,ZuBsPaCe/godot,godotengine/godot,pkowal1982/godot,godotengine/godot,vkbsb/godot,BastiaanOlij/godot,sanikoyes/godot,guilhermefelipecgs/godot,josempans/godot,firefly2442/godot,guilhermefelipecgs/godot,guilhermefelipecgs/godot,godotengine/godot