Crash when showing tooltip of collapsed region

Hi,

I have implemented an outlining source based on RangeOutliningSourceBase and recently added support for pre-processor regions.

When the region is only one empty line and collapsed, the application crashes as soon as the tooltip is shown.

== System.ArgumentException ==
Message:
Width and Height must be non-negative.
Source:
WindowsBase
StackTrace:
at System.Windows.Rect..ctor(Double x, Double y, Double width, Double height)
at ActiproSoftware.Windows.Controls.SyntaxEditor.IntelliPrompt.Implementation.IntelliPromptSessionBase.#Pfc(Boolean #syf)
at ActiproSoftware.Windows.Controls.SyntaxEditor.IntelliPrompt.Implementation.QuickInfoSession.Reposition()
at ActiproSoftware.Windows.Controls.SyntaxEditor.IntelliPrompt.Implementation.QuickInfoSession.OnOpened(EventArgs e)
at ActiproSoftware.Windows.Controls.SyntaxEditor.IntelliPrompt.Implementation.IntelliPromptSessionBase.Open(IEditorView view, TextRange textRange)
at ActiproSoftware.Windows.Controls.SyntaxEditor.IntelliPrompt.Implementation.CollapsedRegionQuickInfoProvider.RequestSession(IEditorView view, Object context)
at ActiproSoftware.Windows.Controls.SyntaxEditor.IntelliPrompt.Implementation.QuickInfoProviderBase.RequestSession(IEditorView view, Object context, Boolean canTrackPointer)
at ActiproSoftware.Windows.Controls.SyntaxEditor.IntelliPrompt.Implementation.QuickInfoProviderBase.#2xk(IEditorView #N5b, InputPointerEventArgs #yhb)
at ActiproSoftware.Windows.Controls.SyntaxEditor.IntelliPrompt.Implementation.QuickInfoProviderBase.#zxk(IEditorView #N5b, InputPointerEventArgs #yhb)
at ActiproSoftware.Windows.Controls.SyntaxEditor.Primitives.EditorView.OnPointerHoverTimerTick()
at ActiproSoftware.Windows.Controls.SyntaxEditor.Implementation.TimerManager.#jDk()
at ActiproSoftware.Windows.Controls.SyntaxEditor.Implementation.TimerManager.#iDk(Object #xhb, Object #yhb)
at System.Windows.Threading.DispatcherTimer.FireTick(Object unused)
at System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
at System.Windows.Threading.ExceptionWrapper.TryCatchWhen(Object source, Delegate callback, Object args, Int32 numArgs, Delegate catchHandler)