assign_indexclass - add error checking for criteria columns

[leppott]

Describe the bug
Fails when doesn't get expected columns for criteria.

To Reproduce
Rename criteria columns in data different from criteria data frame.

Expected behavior
Should get a clean exit and a message with what is wrong. Instead get a hard exit with a generic message (see image).

Screenshots

Additional context
NA

[leppott]

Example code from BCGcalc Shiny app that uses assign_indexclass with some error checking before running the function.