New message for deletion; block dispose is a noop if it's already been deleted

msg/js/zh-hans.js

@@ -63,6 +63,7 @@ Blockly.Msg.CONTROLS_WHILEUNTIL_TOOLTIP_WHILE = "只要值为真，执行一些
 Blockly.Msg.DELETE_ALL_BLOCKS = "删除所有%1块吗？";
 Blockly.Msg.DELETE_BLOCK = "删除块";
 Blockly.Msg.DELETE_VARIABLE = "Delete the '%1' variable";  // untranslated
+Blockly.Msg.DELETE_VARIABLE_CONFIRMATION = "Delete %1 uses of the %2 variable?";  // untranslated
 Blockly.Msg.DELETE_X_BLOCKS = "删除 %1 块";
 Blockly.Msg.DISABLE_BLOCK = "禁用块";
 Blockly.Msg.DUPLICATE_BLOCK = "复制";