jQuery Grid Plugin - jqGrid

On line 8247 of the 4.3.1 non-min source, you split the postdata.

postdata = postdata.split(",");

for( var pk in postdata) {
    if(postdata.hasOwnProperty(pk)) {
        postdata[pk] = $.jgrid.stripPref($t.p.idPrefix, postdata[pk]);
    }
}

postd[idname] = postdata.join();

Now on line 8282, you try to split it again, this throws an error because the object cannot be split

var toarr = [];
toarr = postdata.split(",");

I hand patched in the code below and the error goes away and my code executes as expected. 

toarr = (typeof postdata == "string") ? postdata.split(",") : postdata;

-- Edit

Looks like this is a known issue, I'll use my patch until your patch, sorry for the dup