Fix bug that prevented dropping new courses

amd/src/studyplan-editor-components.js

@@ -1302,6 +1302,13 @@ export default {
                 }
             },
             methods: {
+                trashbin_accepts(type){
+                    if(type.item){
+                        return true;
+                    } else {
+                        return false;
+                    }
+                },
                 countLineLayers(line){
                     // For some optimization, we cache the value of this calculation for about a second
                     // Would be a lot nicer if we could use a computed property for this.....
@@ -1509,7 +1516,7 @@ export default {
                         mode='copy'
                         class='t-item-deletebox text-danger border-danger'
                         @drop='deleteStudyItem'
-                        :accepts-type="['gradable-item','filter-item']"
+                        :accepts-type="trashbin_accepts"
                         ><i class='fa fa-trash'></i>
                     </drop>
                     <span class='control deletable'>
@@ -1960,6 +1967,7 @@ export default {
             },
             methods: {
                 onDrop(event) {
+                    debug.info(event);
                     this.hover.component = null;
                     this.hover.type = null;
 
@@ -1985,7 +1993,7 @@ export default {
                     }
                     else if(event.type.component){
 
-                        if(event.type.type == "course"){
+                        if(event.type.type == "gradable"){
                             call([{
                                 methodname: 'local_treestudyplan_add_studyitem',
                                 args: { 
@@ -2325,7 +2333,7 @@ export default {
                         }}&nbsp;<b-form-select 
                             class=""
                             size="sm" @change="change_span" v-model="value.span">
-                            <b-form-select-option v-for="(n,i) in maxspan" :value='n'
+                            <b-form-select-option v-for="(n,i) in maxspan" :value='n' :key='i'
                             >{{ n }}</b-form-select-option>
                         </b-form-select
                         >&nbsp;{{