Fix - protect marker drag handler

In case when cleanup done in-between

Author: linev

modules/draw/more.mjs

@@ -315,11 +315,13 @@ function drawMarker() {
    this.moveDrag = function(dx, dy) {
       this.dx += dx;
       this.dy += dy;
-      makeTranslate(this.draw_g.select('path'), this.dx, this.dy);
+      if (this.draw_g)
+         makeTranslate(this.draw_g.select('path'), this.dx, this.dy);
    };
 
    this.moveEnd = function(not_changed) {
-      if (not_changed) return;
+      if (not_changed || !this.draw_g)
+         return;
       const mrk = this.getObject();
       let fx = this.svgToAxis('x', this.axisToSvg('x', mrk.fX, this.isndc) + this.dx, this.isndc),
           fy = this.svgToAxis('y', this.axisToSvg('y', mrk.fY, this.isndc) + this.dy, this.isndc);