Created Issue: Assert after canceling new project dialog with a solution already loaded [800]

Not sure how to repro at this time.

```
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Assertion Failed: Abort=Quit, Retry=Debug, Ignore=Continue
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Unexpected exception while processing change: {0}

System.NullReferenceException: Object reference not set to an instance of an object.

at Microsoft.VisualStudioTools.Project.CommonProjectNode.FileSystemChange.ChildDeleted(HierarchyNode child)

at Microsoft.VisualStudioTools.Project.CommonProjectNode.FileSystemChange.ProcessChange()

at Microsoft.VisualStudioTools.Project.CommonProjectNode.OnIdle(Object sender, ComponentManagerEventArgs e)

at Microsoft.VisualStudioTools.Project.CommonProjectNode.OnIdle(Object sender, ComponentManagerEventArgs e)

at Microsoft.VisualStudioTools.Project.CommonProjectPackage.FDoIdle(UInt32 grfidlef)


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Abort Retry Ignore
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```