abuild: avoid division by zero when input is zero for calculating human size for packages

This occurs when building meta packages that do not have any package content.

abuild.in

@@ -1253,7 +1253,7 @@ scan_pkgconfig_depends() {
 # read size in bytes from stdin and show as human readable
 human_size() {
 	awk '{  split("B KB MB GB TB PB", type)
-		for(i=5; y < 1; i--)
+		for(i=5; y < 1 && $1 > 0; i--)
 			y = $1 / (2**(10*i))
 		printf("%.1f %s\n", y, type[i+2]) }'
 }
@@ -2209,4 +2209,3 @@ for i in $install_after; do
 done
 
 cleanup
-