MDL-7778 fixed cancel button failing on some pages (I hope)

lib/form/cancel.php

@@ -27,7 +27,7 @@ class MoodleQuickForm_cancel extends HTML_QuickForm_submit
             $value=get_string('cancel');
         }
         HTML_QuickForm_submit::HTML_QuickForm_submit($elementName, $value, $attributes);
-        $this->updateAttributes(array('onclick'=>'return this.form.submit();'));
+        $this->updateAttributes(array('onclick'=>'skipClientValidation = true; return true;'));
     } //end constructor
     function onQuickFormEvent($event, $arg, &$caller)
     {

lib/formslib.php

@@ -733,6 +733,9 @@ class MoodleQuickForm extends HTML_QuickForm_DHTMLRulesTableless {
         $js = '
 <script type="text/javascript">
 //<![CDATA[
+
+var skipClientValidation = false;
+
 function qf_errorHandler(element, _qfMsg) {
   div = element.parentNode;
   if (_qfMsg != \'\') {
@@ -809,6 +812,9 @@ function validate_' . $this->_attributes['id'] . '_' . $elementName . '(element)
         }
         $js .= '
 function validate_' . $this->_attributes['id'] . '(frm) {
+  if (skipClientValidation) {
+     return true;
+  }
   var ret = true;
 ' . $validateJS . ';
   return ret;