Incorrect relevant conditions in questionnaires not detected when uploading a xlsform

[dpalomino]

Steps to reproduce the error

1. Upload a xlsform with an incorrect relevant condition (for instance $var='asdf' instead of ${var}='asdf')
2. File is accepted
3. From ODK you can download the form and submit records, the relevant condition is just ignored

Actual behavior

See above

Expected behavior

The syntax error should be detected when uploading the file

[dpalomino]

Thanks Brian!

To be fixed prior to the release of Sprint 18.

[amplifi]

@dpalomino This is for a patch release after Sprint 18 release.