Fix map stuff, and implement builtin funcs for it

viewsheets.ts

@@ -26,6 +26,10 @@ const update = () => {
 		if (g) {
 			const {x, y} = g;
 			page.activeSheet = 4*y+x;
+			const sheet = getSheet(page.activeSheet);
+			if (!sheet) {
+				console.log(x, y, g);
+			}
 			page.tab = getSheet(page.activeSheet).sheet_type;
 		}
 	}