Fix backpack behavior in Blockly update

Backpack menu items in the workspace, i.e. Copy All to Backpack and
Paste All From Backpack were broken during the transition to the
latest Blockly. This commit changes any checks for the backpack
presence to use the hasBackpack() test added to WorkspaceSvg.

Change-Id: Iae7919d173f5a5f75003c0132d1f116af9839bd0

appinventor/blocklyeditor/src/backpack.js

@@ -246,7 +246,7 @@ Blockly.Backpack.prototype.pasteBackpack = function() {
     var ok = true;
     for (var j = 0; j < arr.length; j++) {
       var type = arr[j];
-      if (! this.workspace_.getComponentDatabase().hasType(type)) {
+      if (!Blockly.Blocks[type] && ! this.workspace_.getComponentDatabase().hasType(type)) {
         ok = false;
         break;
       }

appinventor/blocklyeditor/src/workspace_svg.js

@@ -673,7 +673,7 @@ Blockly.WorkspaceSvg.prototype.customContextMenu = function(menuOptions) {
     Blockly.getMainWorkspace().getBackpack().count() + ")";
   backpackRetrieve.callback = function() {
     if (Blockly.getMainWorkspace().hasBackpack()) {
-      Blockly.getMainWorkspace().getBackpack().pasteBackpack(this.backpack_);
+      Blockly.getMainWorkspace().getBackpack().pasteBackpack();
     }
   };
   menuOptions.push(backpackRetrieve);
@@ -682,7 +682,7 @@ Blockly.WorkspaceSvg.prototype.customContextMenu = function(menuOptions) {
   var backpackCopyAll = {enabled: true};
   backpackCopyAll.text = Blockly.Msg.COPY_ALLBLOCKS;
   backpackCopyAll.callback = function() {
-    if (this.backpack_) {
+    if (Blockly.getMainWorkspace().hasBackpack()) {
       Blockly.getMainWorkspace().getBackpack().addAllToBackpack();
     }
   };
@@ -692,7 +692,9 @@ Blockly.WorkspaceSvg.prototype.customContextMenu = function(menuOptions) {
   var backpackClear = {enabled: true};
   backpackClear.text = Blockly.Msg.BACKPACK_EMPTY;
   backpackClear.callback = function() {
-    Blockly.getMainWorkspace().getBackpack().clear();
+    if (Blockly.getMainWorkspace().hasBackpack()) {
+      Blockly.getMainWorkspace().getBackpack().clear();
+    }
     backpackRetrieve.text = Blockly.Msg.BACKPACK_GET;
   };
   menuOptions.push(backpackClear);