fix for grouping items with no type

Fixed an error that caused the app to crash when trying to group a bulk set of items when there are items with no "type" property. Items something like "delete request" items had no type.

src/lib/utils.js

@@ -84,6 +84,10 @@ const getPluralType = (type) =>{
   // is not generated in the lookup. this is a
   // kludge around that. (specifically availabilitySummary)
   plural = teamsnap.getPluralType(type) || (function() {
+    if (type === undefined){
+      return type
+    }
+
     switch (type.slice(-1)) {
       case 'y':
         return type.slice(0, -1) + 'ies';