From 713397b0082190f9e44ad6d9f2a2b183bafc8694 Mon Sep 17 00:00:00 2001
From: Brian Geppert <briangeppert@briangeppert.com>
Date: Sun, 7 Dec 2014 19:19:35 -0600
Subject: [PATCH] Don't crash on prompt cancel.

---
 core/field_textinput.js | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/core/field_textinput.js b/core/field_textinput.js
index 714643b14..bebc737db 100644
--- a/core/field_textinput.js
+++ b/core/field_textinput.js
@@ -253,6 +253,9 @@ Blockly.FieldTextInput.prototype.widgetDispose_ = function() {
  * @return {?string} A string representing a valid number, or null if invalid.
  */
 Blockly.FieldTextInput.numberValidator = function(text) {
+  if(text === null) {
+    return null;
+  }
   // TODO: Handle cases like 'ten', '1.203,14', etc.
   // 'O' is sometimes mistaken for '0' by inexperienced users.
   text = text.replace(/O/ig, '0');