Added and tested functionality for including "N/A" in stats output.

[AustinSanders]

Added and tested functionality for including "N/A" in stats output.

Description

In situations in which there are no valid pixels, stats output skipped a variety of stats types. This led to problems in the alignment of columns when output was combined with images that contained valid pixels.

Related Issue

#3870

Motivation and Context

This allows for columns to be populated with "N/A" in situations in which an image contains only special pixels.

How Has This Been Tested?

Functionality was manually tested on the data included in #3870 issue description. Additionally, "stats" ctests were updated

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Documentation change (update to the documentation; no code change)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have read and agree to abide by the Code of Conduct
• I have read the CONTRIBUTING document.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

Licensing

This project is mostly composed of free and unencumbered software released into the public domain, and we are unlikely to accept contributions that are not also released into the public domain. Somewhere near the top of each file should have these words:

This work is free and unencumbered software released into the public domain. In jurisdictions that recognize copyright laws, the author or authors of this software dedicate any and all copyright interest in the software to the public domain.

• I dedicate any and all copyright interest in this software to the public domain. I make this dedication for the benefit of the public at large and to the detriment of my heirs and successors. I intend this dedication to be an overt act of relinquishment in perpetuity of all present and future rights to this software under copyright law.

[AustinSanders]

Closed due to the inclusion of commit 60dbffa. This should not be included.