CanvasModulate: fix build issue with GCC
CanvasModulate: fix build issue with GCC

Bug from c195c0d.

BastiaanOlij/godot,buckle2000/godot,Faless/godot,Faless/godot,groud/godot,iap-mutant/godot,Brickcaster/godot,akien-mga/godot,opmana/godot,DmitriySalnikov/godot,godotengine/godot,josempans/godot,est31/godot,ficoos/godot,Max-Might/godot,JoshuaGrams/godot,Valentactive/godot,pkowal1982/godot,opmana/godot,NateWardawg/godot,morrow1nd/godot,iap-mutant/godot,FateAce/godot,FateAce/godot,groud/godot,sanikoyes/godot,JoshuaGrams/godot,DmitriySalnikov/godot,Valentactive/godot,honix/godot,TheHX/godot,iap-mutant/godot,agusbena/godot,agusbena/godot,iap-mutant/godot,MarianoGnu/godot,azurvii/godot,azurvii/godot,ZuBsPaCe/godot,exabon/godot,quabug/godot,vkbsb/godot,Max-Might/godot,sanikoyes/godot,buckle2000/godot,MrMaidx/godot,firefly2442/godot,NateWardawg/godot,rollenrolm/godot,ex/godot,Valentactive/godot,akien-mga/godot,MarianoGnu/godot,DmitriySalnikov/godot,opmana/godot,Brickcaster/godot,Hodes/godot,DmitriySalnikov/godot,pkowal1982/godot,pkowal1982/godot,gau-veldt/godot,pixelpicosean/my-godot-2.1,agusbena/godot,n-pigeon/godot,pkowal1982/godot,RandomShaper/godot,tomreyn/godot,Zylann/godot,vkbsb/godot,Zylann/godot,huziyizero/godot,jejung/godot,zicklag/godot,Paulloz/godot,est31/godot,pkowal1982/godot,iap-mutant/godot,akien-mga/godot,vnen/godot,JoshuaGrams/godot,FateAce/godot,groud/godot,TheHX/godot,Marqin/godot,morrow1nd/godot,mcanders/godot,buckle2000/godot,DmitriySalnikov/godot,honix/godot,quabug/godot,Hodes/godot,ZuBsPaCe/godot,Marqin/godot,BastiaanOlij/godot,BastiaanOlij/godot,ex/godot,guilhermefelipecgs/godot,Paulloz/godot,Zylann/godot,Valentactive/godot,n-pigeon/godot,okamstudio/godot,akien-mga/godot,Max-Might/godot,MarianoGnu/godot,n-pigeon/godot,josempans/godot,vnen/godot,Hodes/godot,sanikoyes/godot,Hodes/godot,NateWardawg/godot,RebelliousX/Go_Dot,agusbena/godot,TheHX/godot,Zylann/godot,DmitriySalnikov/godot,groud/godot,quabug/godot,huziyizero/godot,vnen/godot,jejung/godot,gau-veldt/godot,Hodes/godot,BastiaanOlij/godot,guilhermefelipecgs/godot,Shockblast/godot,azurvii/godot,pkowal1982/godot,honix/godot,Max-Might/godot,vnen/godot,exabon/godot,n-pigeon/godot,ZuBsPaCe/godot,groud/godot,guilhermefelipecgs/godot,guilhermefelipecgs/godot,gau-veldt/godot,n-pigeon/godot,FateAce/godot,buckle2000/godot,akien-mga/godot,Marqin/godot,exabon/godot,quabug/godot,BastiaanOlij/godot,godotengine/godot,MarianoGnu/godot,groud/godot,quabug/godot,Brickcaster/godot,ex/godot,akien-mga/godot,ageazrael/godot,JoshuaGrams/godot,sanikoyes/godot,jejung/godot,NateWardawg/godot,Faless/godot,TheHX/godot,Brickcaster/godot,ficoos/godot,MrMaidx/godot,azurvii/godot,opmana/godot,quabug/godot,gau-veldt/godot,ZuBsPaCe/godot,jejung/godot,huziyizero/godot,Marqin/godot,iap-mutant/godot,sanikoyes/godot,Faless/godot,firefly2442/godot,exabon/godot,rollenrolm/godot,Shockblast/godot,rollenrolm/godot,honix/godot,iap-mutant/godot,Shockblast/godot,rollenrolm/godot,guilhermefelipecgs/godot,firefly2442/godot,tomreyn/godot,Zylann/godot,vkbsb/godot,Marqin/godot,mcanders/godot,Paulloz/godot,RebelliousX/Go_Dot,BastiaanOlij/godot,vkbsb/godot,ageazrael/godot,n-pigeon/godot,est31/godot,mcanders/godot,huziyizero/godot,okamstudio/godot,RandomShaper/godot,ficoos/godot,Paulloz/godot,Zylann/godot,firefly2442/godot,Max-Might/godot,zicklag/godot,RebelliousX/Go_Dot,sanikoyes/godot,pixelpicosean/my-godot-2.1,Faless/godot,ageazrael/godot,vnen/godot,sanikoyes/godot,RebelliousX/Go_Dot,ageazrael/godot,mcanders/godot,NateWardawg/godot,Paulloz/godot,iap-mutant/godot,godotengine/godot,Zylann/godot,Shockblast/godot,morrow1nd/godot,josempans/godot,vnen/godot,okamstudio/godot,Max-Might/godot,buckle2000/godot,RandomShaper/godot,josempans/godot,morrow1nd/godot,mcanders/godot,Valentactive/godot,josempans/godot,ex/godot,okamstudio/godot,godotengine/godot,Brickcaster/godot,BastiaanOlij/godot,exabon/godot,firefly2442/godot,pkowal1982/godot,quabug/godot,JoshuaGrams/godot,tomreyn/godot,godotengine/godot,huziyizero/godot,okamstudio/godot,RebelliousX/Go_Dot,quabug/godot,okamstudio/godot,ex/godot,ageazrael/godot,NateWardawg/godot,Zylann/godot,guilhermefelipecgs/godot,pkowal1982/godot,firefly2442/godot,RandomShaper/godot,exabon/godot,ageazrael/godot,ZuBsPaCe/godot,azurvii/godot,iap-mutant/godot,pixelpicosean/my-godot-2.1,Shockblast/godot,NateWardawg/godot,okamstudio/godot,vnen/godot,tomreyn/godot,vkbsb/godot,guilhermefelipecgs/godot,Paulloz/godot,rollenrolm/godot,RebelliousX/Go_Dot,MarianoGnu/godot,godotengine/godot,zicklag/godot,vkbsb/godot,vnen/godot,Valentactive/godot,Shockblast/godot,buckle2000/godot,FateAce/godot,okamstudio/godot,BastiaanOlij/godot,MrMaidx/godot,Faless/godot,akien-mga/godot,guilhermefelipecgs/godot,agusbena/godot,sanikoyes/godot,RandomShaper/godot,FateAce/godot,ZuBsPaCe/godot,agusbena/godot,JoshuaGrams/godot,quabug/godot,jejung/godot,agusbena/godot,firefly2442/godot,DmitriySalnikov/godot,zicklag/godot,ficoos/godot,morrow1nd/godot,zicklag/godot,gau-veldt/godot,okamstudio/godot,NateWardawg/godot,MrMaidx/godot,iap-mutant/godot,honix/godot,Valentactive/godot,MarianoGnu/godot,tomreyn/godot,akien-mga/godot,josempans/godot,RandomShaper/godot,RandomShaper/godot,MarianoGnu/godot,josempans/godot,ficoos/godot,pixelpicosean/my-godot-2.1,mcanders/godot,opmana/godot,godotengine/godot,quabug/godot,honix/godot,Hodes/godot,ex/godot,vkbsb/godot,ex/godot,Paulloz/godot,Brickcaster/godot,godotengine/godot,ficoos/godot,okamstudio/godot,ex/godot,est31/godot,azurvii/godot,Valentactive/godot,MarianoGnu/godot,MrMaidx/godot,Shockblast/godot,Brickcaster/godot,Marqin/godot,ZuBsPaCe/godot,vkbsb/godot,firefly2442/godot,Faless/godot,ageazrael/godot,morrow1nd/godot,MrMaidx/godot,n-pigeon/godot,pixelpicosean/my-godot-2.1,zicklag/godot,josempans/godot,NateWardawg/godot,Shockblast/godot,jejung/godot,est31/godot,ZuBsPaCe/godot,TheHX/godot,Faless/godot,est31/godot,agusbena/godot