fix(handler): replace raise e with bare raise and use is None

[Jah-yee]

Summary

Fixes an exception chaining anti-pattern in Handler.getBatchDetailsIter that was masking original tracebacks, and applies PEP 8 style consistency in getBatchDetails.

Changes

1. Replace raise e with bare raise (line 395)

   raise e creates a new exception without preserving the original traceback,
   making debugging significantly harder. Bare raise re-raises the active
   exception while keeping the full chain intact.

2. Use is None instead of == None in getBatchDetails (line 235)

   PEP 8 style consistency — the sibling method getBatchDetailsIter already
   uses is None.

Impact

• Tracebacks from network and HTTP errors are now fully actionable.
• No behaviour change for successful requests or existing callers.

Verification

python3 -m py_compile ipinfo/handler.py   # passes