clean_figure() error when scatter() has 1 point

```python
	import matplotlib.pyplot as plt
	import tikzplotlib
	plt.scatter([-2], [3])
	tikzplotlib.clean_figure()
```


Error:

```python
ValueError: all the input arrays must have same number of dimensions, but the array at index 0 has 1 dimension(s) and the array at index 1 has 2 dimension(s)
```

Probably related to https://github.com/nschloe/tikzplotlib/issues/403.