(JSON) Object parser Browser vs. Client

I am despairing of what I would call a bug.

I have a function (global) that works fine in the browser, but fails in the app and breaks the entire global script.

The problem is to store a JSON object in a list, here to produce a valid GeoJSON with.

features: [{...}]

If I do not enforce this list (but therefore no valid GeoJSON), it is not a problem.

The error indicates that an object is being written to that does not exist.

Here are two attempts, both unsuccessful (in CLI):

Version 1

function make_GeoJSON(ref : Places,JJ : text) do
    let fJ := [{}];
    let gJ := {};
    let pJ := {
            PLACE_ID: number(ref),
PLACE_NAME: ref.Name,
PLACE_TYPE: ref.Type.Name,
            PLACE_TYPE_ID: ref.Type.number(Id),
            distance: 0
        };
    if JJ = "" then JJ := ref.GeoJSON end;
    let J := parseJSON(JJ);
    if cnt(J.features) > 0 then
        fJ := [J.first(features)];
        if ref.'Primary Location' and longitude(ref.'Primary Location') != 0 and
                        latitude(ref.'Primary Location') != 0 and
                    longitude(ref.'Primary Location') and
                latitude(ref.'Primary Location') and
            first(fJ).geometry.type = "Point" then
            setItem(first(fJ).geometry, "coordinates", [longitude(ref.'Primary Location'), latitude(ref.'Primary Location')])
        end;
        if not first(fJ).properties then
            setItem(first(fJ), "properties", pJ)
        end;
        if not first(fJ).properties.distance then
            setItem(first(fJ).properties, "distance", 0)
        end;
        setItem(first(fJ), "id", number(ref));
        setItem(first(fJ).properties, "PLACE_ID", number(ref));
        setItem(first(fJ).properties, "PLACE_NAME", ref.Name);
        setItem(first(fJ).properties, "PLACE_TYPE", ref.Type.Name);
        setItem(first(fJ).properties, "PLACE_TYPE_ID", ref.Type.number(Id));
        setItem(J, "features", fJ)
    else
        void
    end;
    formatJSON(J)
end;

Here is the problem in:

 let fJ := [{}];

Version 2

function make_GeoJSON(ref : Places,JJ : text) do
    let fJ := {};
    let gJ := {};
    let pJ := {
            PLACE_ID: number(ref),
            PLACE_NAME: ref.Name,
            PLACE_TYPE: ref.Type.Name,
            PLACE_TYPE_ID: ref.Type.number(Id),
            distance: 0
        };
    if JJ = "" then JJ := ref.GeoJSON end;
    let J := parseJSON(JJ);
    if cnt(J.features) > 0 then
        fJ := J.first(features);
        if ref.'Primary Location' and longitude(ref.'Primary Location') != 0 and
                        latitude(ref.'Primary Location') != 0 and
                    longitude(ref.'Primary Location') and
                latitude(ref.'Primary Location') and
            fJ.geometry.type = "Point" then
            setItem(fJ.geometry, "coordinates", [longitude(ref.'Primary Location'), latitude(ref.'Primary Location')])
        end;
        if not fJ.properties.distance then
            setItem(fJ.properties, "distance", 0)
        end;
        setItem(fJ, "id", number(ref));
        setItem(fJ.properties, "PLACE_ID", number(ref));
        setItem(fJ.properties, "PLACE_NAME", ref.Name);
        setItem(fJ.properties, "PLACE_TYPE", ref.Type.Name);
        setItem(fJ.properties, "PLACE_TYPE_ID", ref.Type.number(Id));
        setItem(J, "features", [fJ])
    else
        void
    end;
    formatJSON(J)
end;

Here the problem is in

setItem(J, "features", [fJ])

To make it easier to understand, here is a correct GeoJSON:

{"type":"FeatureCollection","features":[{"geometry":{"coordinates":[-1.4440324,40.405312],"type":"Point"},"id":28,"properties":{"PLACE_ID":28,"PLACE_NAME":"Albarracín","PLACE_TYPE":"locality","PLACE_TYPE_ID":55,"distance":1180.7024668824363},"type":"Feature"}]}

PS: And the void in else is not in the original, here only for shortening. In fact, an entire GeoJSON is constructed there instead of being updated.

ref is a record from table Places. Behavior is the same if the script is nested in a local formula.