Adds localhost case to the Player Panel (#79999)

## About The Pull Request


![image](https://github.com/tgstation/tgstation/assets/34697715/2fd2b8fd-dc86-4150-8f0f-b8ac6a5dc03c)

This always confused me debugging on local, the thing in the parenthesis
is supposed to the be the IP Address of the client currently in the mob.
However, local hosts have a `null` IP Address (BYOND thing). So, let's
add handling to this so this little thing won't be so confusing anymore
## Why It's Good For The Game


![image](https://github.com/tgstation/tgstation/assets/34697715/b365e107-cfcf-497c-92da-f5930666cbb0)

Better.
## Changelog
Not really relevant.

code/modules/admin/player_panel.dm

@@ -274,6 +274,8 @@
 				else
 					M_job = "Ghost"
 
+			var/M_ip_address = isnull(M.lastKnownIP) ? "+localhost+" : M.lastKnownIP
+
 			var/M_name = html_encode(M.name)
 			var/M_rname = html_encode(M.real_name)
 			var/M_rname_as_key = html_encode(ckey(M.real_name)) // so you can ignore punctuation
@@ -304,7 +306,7 @@
 						<span hidden id="data[i]_rname_as_key">[M_rname_as_key]</span>
 						<span hidden id="data[i]_prevnames">[previous_names]</span>
 						<span hidden id="data[i]_key">[M_key]</span>
-						<span hidden id="data[i]_lastip">[M.lastKnownIP]</span>
+						<span hidden id="data[i]_lastip">[M_ip_address]</span>
 						<span hidden id="data[i]_isantag">[is_antagonist]</span>
 						<span hidden id="data[i]_ref">[REF(M)]</span>
 						</a>