Fix issue with update_time_lost being called on jira tickets that doesn't have a time lost defined

[sebastian-aranda]

This PR includes updates to the update_time_lost functionality and adds a new test case to ensure proper handling when the time_lost field is None for jira tickets that have not set that field.

Updates to update_time_lost functionality:

• manager/manager/utils.py: Modified the update_time_lost function to handle cases where the time_lost field is None by checking the value before converting it to a float.

New test case:

• manager/api/tests/test_jira.py: Added a new test test_update_current_time_lost_none to verify that the update_time_lost function correctly updates the time_lost field when it is initially None.

[Vebop]

I see how an error could happen with returning None instead of 0.0 with the original code. Good fix.