unchecking a dataset type for a dataset will delete that type from all the other datasets that had it

[rija]

Describe the bug

CONFIRMED
I just tried on staging to remove the Dataset Type Genomic from dataset 102628 and it has removed ALL instances of it.
Incase its relevant, the dataset status was set as "import from EM" 

So we know what the cause of the missing dataset types is, we just need to get it fixed, in the mean time 

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[alli83]

#2147