Missing units prevent plotting

[DunklesArchipel]

When no units are specified in the fields of the entry, the plot method in entry() returns an error

Cell In[7], [line 2](vscode-notebook-cell:?execution_count=7&line=2)
      1 entry = Entry.from_csv(file, header_lines=[2](vscode-notebook-cell:?execution_count=7&line=2))
----> 2 entry.plot()

File d:\github\echemdb\electrochemistry-data\.pixi\envs\dev\Lib\site-packages\unitpackage\entry.py:780, in Entry.plot(self, x_label, y_label, name)
    762 fig = plotly.graph_objects.Figure()
    764 fig.add_trace(
    765     plotly.graph_objects.Scatter(
    766         x=self.df[x_label],
   (...)    770     )
    771 )
    773 fig.update_layout(
    774     template="simple_white",
    775     showlegend=True,
    776     autosize=True,
    777     width=600,
    778     height=400,
    779     margin={"l": 70, "r": 70, "b": 70, "t": 70, "pad": 7},
--> [780](file:///D:/github/echemdb/electrochemistry-data/.pixi/envs/dev/Lib/site-packages/unitpackage/entry.py:780)     xaxis_title=f"{x_label} [{self.field_unit(x_label)}]",
    781     yaxis_title=f"{y_label} [{self.field_unit(y_label)}]",
    782 )
    784 fig.update_xaxes(showline=True, mirror=True)
    785 fig.update_yaxes(showline=True, mirror=True)
...
   (...)    365 
    366     """
--> [367](file:///D:/github/echemdb/electrochemistry-data/.pixi/envs/dev/Lib/site-packages/unitpackage/entry.py:367)     return self.mutable_resource.schema.get_field(field_name).custom["unit"]

KeyError: 'unit'