[GTK] Fix crash
[GTK] Fix crash

Caused by collection change while being iterated.
akrisiun/xwt,lytico/xwt,residuum/xwt,mono/xwt,antmicro/xwt,cra0zy/xwt,steffenWi/xwt,directhex/xwt,mminns/xwt,hwthomas/xwt,TheBrainTech/xwt,mminns/xwt,iainx/xwt,hamekoz/xwt,sevoku/xwt