literalMidWordUnderscores causes full sentences to be bolded

[rachel-church]

I would expect the behavior of literalMidWordUnderscores to only affect underscores attached to non-space characters.

Example:
some text with__underscores__in middle where __ is used without spaces between words.

Actual Behavior:
If literalMidWordUnderscores is true then all text between two separate bolded words gets bolded.

__Once upon a time__, there was a little girl named __Goldilocks__.
Expected: Once upon a time, there was a little girl named Goldilocks.

[tivie]

bug introduced in 1.6.4