Bug COP_file_values

[JonasPfeiffer123]

fname must be a string, a filehandle, a sequence of strings,
or an iterator of strings. Got <class 'NoneType'> instead.
Traceback (most recent call last):
File "...\Programs\Python\Python311\Lib\site-packages\numpy\lib_npyio_impl.py", line 1996, in genfromtxt
fhd = iter(fid)
^^^^^^^^^
TypeError: 'NoneType' object is not iterable

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "...\DistrictHeatingSim\src\districtheatingsim\gui\NetSimulationTab\net_calculation_threads.py", line 130, in run
self.NetworkGenerationData = time_series_preprocessing(self.NetworkGenerationData)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "...\DistrictHeatingSim\src\districtheatingsim\net_simulation_pandapipes\pp_net_time_series_simulation.py", line 299, in time_series_preprocessing
COP_file_values = np.genfromtxt(NetworkGenerationData.COP_filename, delimiter=";")
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "...\Programs\Python\Python311\Lib\site-packages\numpy\lib_npyio_impl.py", line 1998, in genfromtxt
raise TypeError(
TypeError: fname must be a string, a filehandle, a sequence of strings,
or an iterator of strings. Got <class 'NoneType'> instead.