Input Parsing Error claiming there is missing fret when using a different character for pull offs

[chrismoon-code]

Version: 0.3.0
Platform: Windows 10
Reproduction:
Load the following text file TabExample.txt. Modify the tablature by changing the p with the letter c and d. Click on the convert and Save button.
Expected: Error addressing improper formatting in the tablature
Actual: receive an error claiming that there is a missing fret where the character c or d is placed.
Priority: Low
Severity Low - prevents the improper tablature from being created but the error message is misleading to the user.
Screenshot: