fix(rnstatus): Add validation for missing -i flag when using -R

Add check to ensure `management_identity` is provided when using remote
query flag (`-R`). Prevents `TypeError` and provides clear error message
when user forgets to specify identity file with `-i` flag.

Before: `expected str, bytes or os.PathLike object, not NoneType`
After: `Remote management requires an identity file. Use -i to specify the path to a management identity.`

Fixes #792

RNS/Utilities/rnstatus.py

@@ -168,6 +168,9 @@ def program_setup(configdir, dispall=False, verbosity=0, name_filter=None, json=
     stats = None
     if remote:
         try:
+            if management_identity is None:
+                raise ValueError("Remote management requires an identity file. Use -i to specify the path to a management identity.")
+
             dest_len = (RNS.Reticulum.TRUNCATED_HASHLENGTH//8)*2
             if len(remote) != dest_len:
                 raise ValueError("Destination length is invalid, must be {hex} hexadecimal characters ({byte} bytes).".format(hex=dest_len, byte=dest_len//2))