[BUG-REPORT] Vaex `to_dask_array` fails `AttributeError: 'ValueError' object has no attribute 'numpy'`

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Description Please provide a clear and concise description of the problem. This should contain all the steps needed to reproduce the problem. A minimal code example that exposes the problem is very appreciated.

Software information

• Vaex version (import vaex; vaex.__version__): {'vaex-core': '4.8.0', 'vaex-hdf5': '0.11.1'}
• Vaex was installed via: pip / conda-forge / from source pip
• OS: MacOS

Additional information Please state any supplementary information or provide additional context for the problem (e.g. screenshots, data, etc..).

import vaex

def tolist(x,y):
    return list([x,y])

data = {'A':[1,2,1],'B':['a','b','c'], 'C':['d', 'e', 'f']}
df = vaex.from_dict(data)
df.to_dask_array()