Indicator reports task start times as the 'Due by' time

### What Happened?

When a task has both a start time and a due time set (e.g. in another CalDAV app such as Tasks.org), the date & time indicator reports each task as being 'due by' the start time. In the main Tasks application, the due time is reported correctly.

Tasks in the panel indicator (incorrect):


The same tasks in the Tasks application (correct):


### Steps to Reproduce

1. Create a task with a start date and a due date & time in Tasks.org, or any other CalDAV app that allows this
2. Synchronize the task to Elementary OS, check the date & time indicator

### Expected Behavior

The indicator should report the due time as the 'Due by' time, not the start time.

### OS Version

6.x (Odin)

### Software Version

Latest release (I have run all updates)