Fix black blockly background on IE.
Fix black blockly background on IE.

SoftwareEngineeringToolDemos/FSE-2012-TouchDevelop,CodeKingdomsTeam/TouchDevelop,jmptrader/TouchDevelop,MetSystem/TouchDevelop,UIKit0/TouchDevelop,sedouard/TouchDevelop,Aksoom-Hussain/TouchDevelop,ntoll/TouchDevelop,jle33/TouchDevelop,imadityab/FSE-2012-TouchDevelop-old,CodeKingdomsTeam/TouchDevelop,SoftwareEngineeringToolDemos/FSE-2012-TouchDevelop,SoftwareEngineeringToolDemos/FSE-2012-TouchDevelop,CodeKingdomsTeam/TouchDevelop,imadityab/FSE-2012-TouchDevelop-old,Aksoom-Hussain/TouchDevelop,CodeKingdomsTeam/TouchDevelop,jle33/TouchDevelop,imadityab/FSE-2012-TouchDevelop-old,imadityab/FSE-2012-TouchDevelop-old,SoftwareEngineeringToolDemos/FSE-2012-TouchDevelop,Aksoom-Hussain/TouchDevelop,UIKit0/TouchDevelop,SoftwareEngineeringToolDemos/FSE-2012-TouchDevelop,MetSystem/TouchDevelop,SoftwareEngineeringToolDemos/FSE-2012-TouchDevelop,UIKit0/TouchDevelop,jmptrader/TouchDevelop,jle33/TouchDevelop,jle33/TouchDevelop,MetSystem/TouchDevelop,sedouard/TouchDevelop,sedouard/TouchDevelop,jmptrader/TouchDevelop,ntoll/TouchDevelop,ntoll/TouchDevelop,jle33/TouchDevelop,jmptrader/TouchDevelop,SoftwareEngineeringToolDemos/FSE-2012-TouchDevelop