Fix errors associated with ctCheck when one cell type passes QC

[sof202]

Description

This pull request will fix the crash that occurs when the pairs() plotting function is called in ctCheck.rmd when only one cell type passes QC (requires >1 column in the matrix used). In the event that only one cell type passes QC, a message will be sent to the error file.

Small problem

The method in which the program determines that only one cell type passes QC is not the best. It specifically is checking if mahDistPCA has only one column (as this is what breaks the pairs() function call). However, this isn't very readable as the test isn't testing the source of the problem (only one cell type), but a consequence of it (mahDistPCA only has one column). This should be refactored at some point, but I have no idea what is happening in these files.

Issue ticket number

This pull request is to address issue: #290.

Type of pull request

• Bug fix
• New feature/enhancement
• Code refactor
• Documentation update

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have tested my code to check that it is functional
• I have used linters to check for common sources of errors
• I have implemented fail safes in my code to account for edge cases
• I have made the corresponding changes to the documentation