Old UI-file leftovers cause newer Qt Designer to crash when loading the UI-file

When we switched from an older Qt version to 4.7.0 some
UI-files didn't open anymore with the Qt Designer. I tried
to pinpoint the reason and I found that certain data
inside designerdata-tag caused the newer Qt Designer to
crash when loading the UI-file. Here's the offending tag:

 <designerdata>
  <property name="gridDeltaY" >
   <number>0</number>
  </property>
  <property name="gridSnapX" >
   <bool>true</bool>
  </property>
 </designerdata> 

I've attached an example UI-file that crashes (test.ui).