applied Hiltjo's multimon mouse-based resize fix

dwm.c

@@ -1365,8 +1365,8 @@ resizemouse(const Arg *arg) {
 		case MotionNotify:
 			nw = MAX(ev.xmotion.x - ocx - 2 * c->bw + 1, 1);
 			nh = MAX(ev.xmotion.y - ocy - 2 * c->bw + 1, 1);
-			if(snap && nw >= selmon->wx && nw <= selmon->wx + selmon->ww
-			&& nh >= selmon->wy && nh <= selmon->wy + selmon->wh)
+			if(snap && c->mon->wx + nw >= selmon->wx && c->mon->wx + nw <= selmon->wx + selmon->ww
+			&& c->mon->wy + nh >= selmon->wy && c->mon->wy + nh <= selmon->wy + selmon->wh)
 			{
 				if(!c->isfloating && selmon->lt[selmon->sellt]->arrange
 				&& (abs(nw - c->w) > snap || abs(nh - c->h) > snap))