Update ToolPathUtil.cs
Update ToolPathUtil.cs

Prevent exception and thus incorrect MSbuild error when LocalPath is null (the default)
jricke/msbuildtasks,loresoft/msbuildtasks,stimpy77/msbuildtasks,wrozmiarek/msbuildtasks,AArnott/msbuildtasks,arekbee/msbuildtasks,smallkid/msbuildtasks