fix last extruder deletion

js/kiri-init.js

@@ -542,6 +542,7 @@ var gs_kiri_init = exports;
 
             // add extruder selection buttons
             if (dev.extruders) {
+                dev.internal = 0;
                 let selext = $('sel-ext');
                 selext.innerHTML = '';
                 let arr = [];

js/kiri.js

@@ -1371,6 +1371,7 @@ self.kiri.copyright = exports.COPYRIGHT;
             UI.extDel.disabled = device.extruders.length < 2;
             UI.extDel.onclick = function() {
                 device.extruders.splice(device.internal,1);
+                device.internal = Math.min(device.internal, device.extruders.length-1);
                 updateExtruderFields(device);
             };
             UI.extAdd.onclick = function() {