prevent_initial_call in callback throws exception [BUG]

[rpmchale]

Thank you so much for helping improve the quality of Dash!

We do our best to catch bugs during the release process, but we rely on your help to find the ones that slip through.

Describe your context
Please provide us your environment so we can easily reproduce the issue.

• replace the result of pip list | grep dash below

dash                      1.15.0
dash-bootstrap-components 0.9.2
dash-core-components      1.11.0
dash-html-components      1.1.0
dash-renderer             1.7.0
dash-table                4.10.0

Describe the bug

With the release of Dash 1.15.0. Setting prevent_initial_call in a callback now throws an exception.
It appears prevent_initial_call must be explicitly provided as a named parameter ex. prevent_initial_call=True. This was not previously the case if all parameters (Output, Input, State, and prevent_initial_call) were provided.

File "C:\Program Files\Python36\lib\site-packages\dash\dash.py", line 980, in callback
_args, _kwargs
File "C:\Program Files\Python36\lib\site-packages\dash\dependencies.py", line 159, in handle_callback_args
prevent_initial_call = args.pop()
AttributeError: 'tuple' object has no attribute 'pop'

Expected behavior

An exception should not be thrown.

[alexcjohnson]

Thanks @rpmchale - confirmed. I think I see another issue in handle_callback_args as well. We'll get this fixed!