Remove redundant (and incorrect) length set. (#256)

* Remove redundant (and incorrect) length set.

Fixes issue #255

* Simplify code by using push instead of a variable

editor/svgcanvas.js

@@ -1108,17 +1108,14 @@ const selectOnly = this.selectOnly = function (elems, showGrips) {
   if (!elemsToRemove.length) { return; }
 
   // find every element and remove it from our array copy
-  let j = 0;
   const newSelectedItems = [],
     len = selectedElements.length;
-  newSelectedItems.length = len;
   for (let i = 0; i < len; ++i) {
     const elem = selectedElements[i];
     if (elem) {
       // keep the item
       if (!elemsToRemove.includes(elem)) {
-        newSelectedItems[j] = elem;
-        j++;
+        newSelectedItems.push(elem);
       } else { // remove the item and its selector
         selectorManager.releaseSelector(elem);
       }