fix issue on failed drag makes the whole grid unresponsive (#2672)

* fix issue on failed drag, shouldn't throw an error

* move the code to orinal position, use optional chaining instead

Author: mustafamilyas

src/gridstack.ts

@@ -2252,7 +2252,7 @@ export class GridStack {
           this.engine.cleanupNode(node); // removes all internal _xyz values
           node.grid = this;
         }
-        delete node.grid._isTemp;
+        delete node.grid?._isTemp;
         dd.off(el, 'drag');
         // if we made a copy ('helper' which is temp) of the original node then insert a copy, else we move the original node (#1102)
         // as the helper will be nuked by jquery-ui otherwise. TODO: update old code path

src/utils.ts

@@ -111,9 +111,9 @@ export class Utils {
 
   /** true if we should resize to content. strict=true when only 'sizeToContent:true' and not a number which lets user adjust */
   static shouldSizeToContent(n: GridStackNode | undefined, strict = false): boolean {
-    return n?.grid && (strict ? 
-    (n.sizeToContent === true || (n.grid.opts.sizeToContent === true && n.sizeToContent === undefined)) :
-    (!!n.sizeToContent || (n.grid.opts.sizeToContent && n.sizeToContent !== false)));
+    return n?.grid && (strict ?
+      (n.sizeToContent === true || (n.grid.opts.sizeToContent === true && n.sizeToContent === undefined)) :
+      (!!n.sizeToContent || (n.grid.opts.sizeToContent && n.sizeToContent !== false)));
   }
 
   /** returns true if a and b overlap */