new USFM crash

[johnml1135]

For Engine 67670ddcdf523878b567e8f1...

Serval.Machine.Shared.Services.PreprocessBuildJob[0]
      Build faulted (67670e60df523878b567e904)
      System.InvalidOperationException: An error occurred while parsing the text 'EXO' in project 'ABC'. Verse: EXO :0, line: 421, character: 31, error: 'Stack empty.'
       ---> System.InvalidOperationException: Stack empty.
         at System.Collections.Generic.Stack`1.ThrowForEmptyStack()
         at SIL.Machine.Corpora.UsfmTextBase.TextRowCollector.EndVerseText(UsfmParserState state, IReadOnlyList`1 scriptureRefs)
         at SIL.Machine.Corpora.ScriptureRefUsfmParserHandlerBase.Verse(UsfmParserState state, String number, String marker, String altNumber, String pubNumber)
         at SIL.Machine.Corpora.UsfmParser.ProcessToken()

[Enkidu93]

Is this a test project or have you intentionally obscured the project name?

[johnml1135]

I'm checking it out now. I'll post more data here soon (yes, I obscured the project name because I don't know if it is sensitive or not).

[johnml1135]

Minimum USFM to reproduce:

\id MAT - Test
\c 1
1 This is the 1\v 00 verse.

[johnml1135]

@Enkidu93 - I was able to identify the issue and make it reproducable (see https://github.com/sillsdev/machine/tree/usfm_error_589). Can you bring this to completion?