Crash on click on Statistics if there is a task that has been worked on, then truely deleted

[amogorkon]

File "F:\Dropbox (Privat)\code\watnu\master\src\watnu\main.py", line 175, in statistics
win_statistics = Statistics()
File "F:\Dropbox (Privat)\code\watnu\master\src\watnu\main.py", line 2381, in init
item = QtWidgets.QTableWidgetItem(typed(inner_query.value, 0, str))
File "F:\Dropbox (Privat)\code\watnu\master\src\watnu\classes.py", line 76, in typed
assert type(res) is kind, f"'{res}' ({type(res)}) is not {kind}! {filename, line_number, function_name}"
AssertionError: 'None' (<class 'NoneType'>) is not <class 'str'>! ('main', 2381, 'init')

[amogorkon]

There's a problem with the cascade on delete in sessions. I guess the next best solution is to clear all sessions that have no existing task_id on clearing deleted tasks.