Minor updates to string helper

amd/src/modedit-modal.js

@@ -17,8 +17,8 @@ export default {
 
         let strings = load_strings({
             editmod: {
-                save$core: "save",
-                cancel$core: "unknown",
+                save$core: "save$core",
+                cancel$core: "cancel$core",
             }
         });
 

amd/src/string-helper.js

@@ -8,7 +8,8 @@ import {get_strings} from 'core/str';
 export function load_strings(strings){
     for(let idx in strings){
         let stringkeys = [];
-        for(const key in  strings[idx]){
+        for(const handle in  strings[idx]){
+            const key = strings[idx][handle];
             let parts = key.split("$");
             let identifier = parts[0];
             let component = (parts.length > 1)?parts[1]:'local_treestudyplan';