fancytree filter node numeric name only

Question

I'm using fancytree I have an issue with the filter when a node name is only a number like an image below

When I try to search for 700264 I got this error in the console and I have no idea if I do something wrong or if it is a bug

Filter settings

$("#treeMU").fancytree({
    extensions: ["filter"],
    quicksearch: true,
    checkbox: true,  // optional
    keyboard: true,  // Support keyboard navigation
    source: {
        url: "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX",
        
    },
    filter: {  // override default settings
       
        autoExpand: true,          // Expand all branches that contain matches while filtered
        counter: true,             // Show a badge with number of matching child nodes near parent icons
        hideExpandedCounter: true, // Hide counter badge if parent is expanded
        hideExpanders: true,       // Hide expanders if all child nodes are hidden by filter
        nodata: true,              // Display a 'no data' status node if result is empty
        mode: "hide"               // Grayout unmatched nodes (pass "hide" to remove unmatched node instead)
     
    },          
  });

Search Input

$("#TreeSearchMU").keypress(function(e){
   if(e.which == 13)  // the enter key code
   {
     $.ui.fancytree.getTree("#treeMU").filterBranches($("#TreeSearchMU").val());
   }  
  
});

When I try add any string character to node name (dot, comma, space, etc...) to be like

The filter is working fine with string character.

Anyone knows what happened and why filter work with string character and does not work with a numeric name?

Environment

• Browser type and version: Google Chrom Version 94.0.4606.61
• jQuery versions: 3.5.1
• Fancytree version: 2.38.0 enabled/affected extensions: filter

Thanks for all.