fix(behavior): guard log_activity against unset logger

[SAY-5]

Description

Fixes #7.

RPPorts arms GPIO Lick/Proximity callbacks in __init__, but Behavior.logger is only set later in Behavior.setup(). A buffered edge between those two points fires the callback while self.logger is still None, and log_activity crashes on self.logger.logger_timer.elapsed_time() / self.logger.trial_key. RPi.GPIO swallows the exception on its C thread, the session continues, and the event is silently dropped.

This guards the early-fire window: if self.logger is unset, log a warning and return the activity time without touching self.logger.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update

How Has This Been Tested?

Added test_log_activity_before_logger_setup in tests/test_behavior.py. It sets behavior.logger = None and asserts log_activity returns the activity time instead of raising AttributeError.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes