MOLD/FLAT on object values does not remove line breaks

[Oldes]

Current behaviour:

>> o
== make object! [
    a: [1 2
        3 4
    ]
]

>> mold/flat o
== {make object! [
a: [1 2
3 4
]
]}

Expected result (like in Red):

>> mold/flat o
== "make object! [a: [1 2 3 4]]"