Underscore breaks Label - see Text Input Controls scenario

[tznind]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. Launch Text Input Controls Scenario
2. Type _- (underscore minus)
3. See crash

Error appears to be in Label hotkey draw logic

Expected behavior
No crash

Screenshots

System.ArgumentOutOfRangeException
  HResult=0x80131502
  Message=Specified argument was out of the range of valid values. (Parameter 'ch')
  Source=System.Private.CoreLib
  StackTrace:
   at System.ThrowHelper.ThrowArgumentOutOfRangeException(ExceptionArgument argument) in System\ThrowHelper.cs:line 259
   at System.Text.Rune.op_Explicit(Char ch) in System.Text\Rune.cs:line 127
   at Terminal.Gui.TextFormatter.RemoveHotKeySpecifier(String text, Int32 hotPos, Rune hotKeySpecifier) in D:\Repos\temp\gui.cs\Terminal.Gui\Text\TextFormatter.cs:line 2127
   at Terminal.Gui.TextFormatter.GetLines() in D:\Repos\temp\gui.cs\Terminal.Gui\Text\TextFormatter.cs:line 607
   at Terminal.Gui.TextFormatter.Draw(Rectangle screen, Attribute normalColor, Attribute hotColor, Rectangle maximum, IConsoleDriver driver) in D:\Repos\temp\gui.cs\Terminal.Gui\Text\TextFormatter.cs:line 78
   at Terminal.Gui.View.DrawText() in D:\Repos\temp\gui.cs\Terminal.Gui\View\View.Drawing.cs:line 423
   at Terminal.Gui.View.DoDrawText() in D:\Repos\temp\gui.cs\Terminal.Gui\View\View.Drawing.cs:line 391
   at Terminal.Gui.View.Draw() in D:\Repos\temp\gui.cs\Terminal.Gui\View\View.Drawing.cs:line 84
   at Terminal.Gui.View.DrawSubviews() in D:\Repos\temp\gui.cs\Terminal.Gui\View\View.Drawing.cs:line 535
   at Terminal.Gui.View.DoDrawSubviews() in D:\Repos\temp\gui.cs\Terminal.Gui\View\View.Drawing.cs:line 496
   at Terminal.Gui.View.Draw() in D:\Repos\temp\gui.cs\Terminal.Gui\View\View.Drawing.cs:line 79
   at Terminal.Gui.View.Draw(IEnumerable`1 views, Boolean force) in D:\Repos\temp\gui.cs\Terminal.Gui\View\View.Drawing.cs:line 24
   at Terminal.Gui.Application.LayoutAndDraw(Boolean forceDraw) in D:\Repos\temp\gui.cs\Terminal.Gui\Application\Application.Run.cs:line 519
   at Terminal.Gui.Application.RunIteration(RunState& state, Boolean firstIteration) in D:\Repos\temp\gui.cs\Terminal.Gui\Application\Application.Run.cs:line 596
   at Terminal.Gui.Application.RunLoop(RunState state) in D:\Repos\temp\gui.cs\Terminal.Gui\Application\Application.Run.cs:line 557
   at Terminal.Gui.Application.Run(Toplevel view, Func`2 errorHandler) in D:\Repos\temp\gui.cs\Terminal.Gui\Application\Application.Run.cs:line 425
   at UICatalog.Scenarios.Text.Main() in D:\Repos\temp\gui.cs\UICatalog\Scenarios\Text.cs:line 447
   at UICatalog.UICatalogApp.UICatalogMain(Options options) in D:\Repos\temp\gui.cs\UICatalog\UICatalog.cs:line 393
   at UICatalog.UICatalogApp.Main(String[] args) in D:\Repos\temp\gui.cs\UICatalog\UICatalog.cs:line 207