Aggregate - start date missing

[leppott]

Describe the bug
After aggregate files the start date is sometimes missing.

To Reproduce
Steps to reproduce the behavior:

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior
Should always have a value. NA and blank not allowed.

Additional context
After update to change from Append # to using actual start and end dates.

Suspect code uses first and last entry. If those are blank then nothing is added in the file name. Ensure have no NA or blanks before using the record.