[miso466]

Summary

Fix three related runtime crash paths in src/khoj/routers/helpers.py::generate_summary_from_files:

1. TypeError: 'NoneType' object is not iterable on empty-agent file summaries:
   When an agent has no existing indexed entries (file_objects is None) but the user uploads/provides a file to summarize (query_files is set), the outer guard at line 780 passes as intended:

   if (file_objects and len(file_objects) == 0 and not query_files) or (not file_objects and not query_files):

   However, lines 785 and 793 attempt to iterate over file_objects directly:

   contextual_data = " ".join([f"File: {file.file_name}\n\n{file.raw_text}" for file in file_objects])
   file_names = [file.file_name for file in file_objects]

   This causes a runtime TypeError: 'NoneType' object is not iterable. Initializing file_objects = file_objects or [] resolves this.

2. TypeError: 'NoneType' object is not callable when send_status_func is None:
   send_status_func has default None in the function signature, but line 801 called it unconditionally without checking if send_status_func:. Aligned with sibling functions in helpers.py (lines 835, 853, 1083, 1101, 1364) by wrapping with if send_status_func:.

3. UnboundLocalError in outer exception handler:
   Line 818 attempted to yield result. result is only defined within the async for result in send_status_func(...) loop. When an exception occurs prior to or without status streaming, result is unbound, raising UnboundLocalError: cannot access local variable 'result' where it is not associated with a value. Corrected to yield response_log.

Verification

• Created reproducer unit test suite exercising:
  • Summary with only query_files when file_objects is None -> passes and generates summary cleanly.
  • Summary with send_status_func -> properly streams status events.
  • Empty files and empty query_files -> returns early with "Sorry, I couldn't find anything to summarize.".
  • Exception handler path -> yields response_log without raising UnboundLocalError.
• Verified python3 -m py_compile src/khoj/routers/helpers.py passes cleanly.