Unhelpful exception thrown when invalid namespace specified in access widener

[Stuff-Stuffs]

If you put an incorrect namespace in an access widener(ex. Named instead of named) the following error gets thrown: Failed to provide net.fabricmc:yarn:1.16-rc1+build.8 : null
This is improved somewhat if you enable the stacktrace
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[modmuss50]

Log is dead, please open an new issue if this is still the case.