Patching a dictionary within a json update the dictionary

[tcezard]

When we update the results of fastqscreen from

uniq hits: { 
    "Homo sapiens": 300,
    "Mus musculus": 200
}

and the PATCH is

uniq hits: { 
    "Homo sapiens": 400,
    "Canis familiaris": 50
}

then the results is:

uniq hits: { 
    "Homo sapiens": 400,
    "Canis familiaris": 50,
    "Mus musculus": 200
}

Which seems wrong.
We could PATCH with

uniq hits: { 
    "Homo sapiens": 400,
    "Canis familiaris": 50,
    "Mus musculus": 0
}

in analysis driver to avoid the issue but that means we will have to add all the species