ECOD does not accept missing data and pandas Series

[enryH]

• detect_outliers_ecod should be called with an numpy nd.array - if a pandas.Series is passed this should be handled as item access works with iloc:

growthcurves/src/growthcurves/preprocessing.py

Lines 260 to 261 in 8709aec

	d = np.diff(N, prepend=N[0])
	X = np.column_stack([np.abs(residual), N, d])

```python 
d = np.diff(N, prepend=N[0])
```

• add test for pandas Series case
• add test with missing values and capture error