Stop calling onchange on deleted blocks.

blocks/logic.js

@@ -310,13 +310,9 @@ Blockly.Blocks['logic_compare'] = {
    * @this Blockly.Block
    */
   onchange: function() {
-    if (!this.workspace) {
-      // Block has been deleted.
-      return;
-    }
     var blockA = this.getInputTargetBlock('A');
     var blockB = this.getInputTargetBlock('B');
-    // Kick blocks that existed prior to this change if they don't match.
+    // Disconnect blocks that existed prior to this change if they don't match.
     if (blockA && blockB &&
         !blockA.outputConnection.checkType_(blockB.outputConnection)) {
       // Mismatch between two inputs.  Disconnect previous and bump it away.
@@ -445,14 +441,10 @@ Blockly.Blocks['logic_ternary'] = {
    * @this Blockly.Block
    */
   onchange: function() {
-    if (!this.workspace) {
-      // Block has been deleted.
-      return;
-    }
     var blockA = this.getInputTargetBlock('THEN');
     var blockB = this.getInputTargetBlock('ELSE');
     var parentConnection = this.outputConnection.targetConnection;
-    // Kick blocks that existed prior to this change if they don't match.
+    // Disconnect blocks that existed prior to this change if they don't match.
     if ((blockA || blockB) && parentConnection) {
       for (var i = 0; i < 2; i++) {
         var block = (i == 1) ? blockA : blockB;

blocks/loops.js

@@ -295,12 +295,8 @@ Blockly.Blocks['controls_flow_statements'] = {
    * @this Blockly.Block
    */
   onchange: function() {
-    if (!this.workspace) {
-      // Block has been deleted.
-      return;
-    }
     var legal = false;
-    // Is the block nested in a control statement?
+    // Is the block nested in a loop?
     var block = this;
     do {
       if (block.type == 'controls_repeat' ||

blocks/procedures.js

@@ -733,10 +733,6 @@ Blockly.Blocks['procedures_ifreturn'] = {
    * @this Blockly.Block
    */
   onchange: function() {
-    if (!this.workspace) {
-      // Block has been deleted.
-      return;
-    }
     var legal = false;
     // Is the block nested in a procedure?
     var block = this;