BUG: invalid parameter functions when (incomplete) user input combined with defaults

[han16nah]

Description

There are invalid parameter functions when (incomplete) user input is combined with defaults.
Example: User provides only size = "small" for car, see here:

co2calculator/tests/unit/test_parameters.py

Line 66 in 23e0d16

def test_emission_factors_car(emission_factors_test) -> None:

[redfrexx]

In PR #192 static error messages were added that catch these errors. However, these will have to be changed if the factors in the csv file are changed. So for now it's good. If necessary find a more flexible solution in the future.