Fix 'FileNotFound' exception when a debugger is not present

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Fixes the following error:

Application: _JitMagic.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.IO.FileNotFoundException
   at System.Drawing.Icon.ExtractAssociatedIcon(System.String, Int32)
   at JitMagic.JitMagic.PopulateJitDebuggers(Architecture)
   at JitMagic.JitMagic..ctor(System.String[])
   at JitMagic.Program.Main(System.String[])

This occurs at startup when the default config is used, but one of the debuggers is not found