fix checkboxes (vm part)

Author: CST1229

src/engine/blocks.js

@@ -668,7 +668,7 @@ class Blocks {
      */
     changeBlock (args) {
         // Validate
-        if (['field', 'mutation', 'checkbox'].indexOf(args.element) === -1) return;
+        if (['field', 'mutation', 'shadow', 'checkbox'].indexOf(args.element) === -1) return;
         let block = this._blocks[args.id];
         if (typeof block === 'undefined') return;
         switch (args.element) {
@@ -721,6 +721,9 @@ class Blocks {
         case 'mutation':
             block.mutation = mutationAdapter(args.value);
             break;
+        case 'shadow':
+            block.shadow = args.value;
+            break;
         case 'checkbox': {
             // A checkbox usually has a one to one correspondence with the monitor
             // block but in the case of monitored reporters that have arguments,