Fix sprites in drop-down (#94)

* Update blocks.js

src/lib/blocks.js

@@ -43,7 +43,7 @@ module.exports = function (vm) {
             if (!vm.runtime.targets.hasOwnProperty(targetId)) continue;
             if (vm.runtime.targets[targetId].isOriginal) {
                 if (!vm.runtime.targets[targetId].isStage) {
-                    if (vm.runtime.targets[targetId].sprite.id === vm.editingTarget.sprite.id) {
+                    if (vm.runtime.targets[targetId] === vm.editingTarget) {
                         continue;
                     }
                     sprites.push([vm.runtime.targets[targetId].sprite.name, vm.runtime.targets[targetId].sprite.name]);