fix(accounts): properly compute $$treeLevel

This commit ensures the $$treeLevel is properly computed by checking if
the account depth is undefined and assigning it -1 if so.  When the tree
level is not properly defined, the grouping in the accounts management
module breaks.

Closes Third-Culture-Software#2433.

client/src/modules/accounts/AccountGrid.js

@@ -41,7 +41,6 @@ function AccountGridService(AccountStore, Accounts, Store, Languages, $httpParam
       this._store = result;
 
       // order and expose data made available through the store
-      // this.data = Accounts.order(this._store.data);
       this.formatStore();
 
       // update exposed store driven data

client/src/modules/accounts/accounts.js

@@ -141,7 +141,6 @@ function AccountsController($rootScope, $timeout, AccountGrid, Notify, Constants
 
   function bindGridData() {
     vm.gridOptions.data = vm.Accounts.data;
-    console.log('vm.Accounts.data', vm.gridOptions.data);
   }
 
   function toggleLoadingIndicator() {

client/src/modules/accounts/accounts.service.js

@@ -130,7 +130,7 @@ function AccountService(Api, bhConstants) {
    */
   function flatten(_tree, _depth) {
     var tree = _tree || [];
-    var depth = Number.isNaN(_depth) ? -1 : _depth;
+    var depth = (!angular.isDefined(_depth) || Number.isNaN(_depth)) ? -1 : _depth;
     depth += 1;
 
     function handleTreeLevel(array, node) {