Small consistency fixes for spaces and FFTOperators.

4 jobs for space_without_dtype_2 in 10 minutes and 16 seconds (queued for 3 seconds)
Status Name Job ID Coverage
  Test
passed test_min #163269

00:01:16

passed test_mpi #163270

00:02:28

passed test_mpi_fftw #163271

00:02:47

passed test_mpi_fftw_hdf5 #163272

00:03:43

45.0%