Radio Reference Import - Temporary Site With Invalid County ID

[DSheirer]

sdrtrunk Version
master

Describe the bug
When users try to access this North Carolina, Mecklenberg County UASI system, the editor shows an API error: https://www.radioreference.com/db/sid/6561

as described here: https://forums.radioreference.com/threads/sdr-trunk-rr-import.465400/#post-3921382

On investigation, there is a new 'TEMP' site that's been added to the system that is reporting a county ID value of 99,999. On attempting to retrieve the county info for that county ID, we get a null response and therefore produce an error.

Email submitted to RR asking of 99,999 is a sentinel value indicating a 'no county' identifier.

Expected behavior
If 99,999 is a sentinel value indicating 'No County', then update SystemEditor:297 to exclude the query when the county ID value is 99,999 or when the value is not greater than zero.