text: Title: [BUG-REPORT] Vaex `to_dask_array` fails `AttributeError: 'ValueError' object has no attribute 'numpy'`
  Body: Thank you for reaching out and helping us improve Vaex!
  
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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()
  ```
  