Do not delete items with null values from database!

[Krot Eval]

Incorrect condition!

https://github.com/akaunting/setting/blob/master/src/Drivers/Database.php#L171

Test:

$insertData[$key] = null;
isset($insertData[$key]); // === false

Better use array_key_exists() instead isset()
Because null is cortrect value!

#43

[Denis Dulici]

Feel free to contribute.

[Krot Eval]

@denisdulici why did you close? Issue not resolved! dislike for you!