Thing create: Fix bridge can't be selected (#2354)

Regression from #2329.

Signed-off-by: Florian Hotze <florianh_dev@icloud.com>

bundles/org.openhab.ui/web/src/components/thing/thing-general-settings.vue

@@ -26,7 +26,7 @@
               This type of Thing needs to be associated to a working Bridge to function properly.
             </f7-block-footer>
             <f7-list v-if="ready && thingType.supportedBridgeTypeUIDs.length" inline-labels no-hairlines-md>
-              <thing-picker v-if="thing.editable"
+              <thing-picker v-if="editable"
                             title="Bridge" name="bridge" :value="thing.bridgeUID"
                             @input="updateBridge"
                             :filterType="thingType.supportedBridgeTypeUIDs" />
@@ -49,6 +49,11 @@ export default {
     ThingPicker,
     ClipboardIcon
   },
+  computed: {
+    editable () {
+      return this.createMode || (this.thing && this.thing.editable)
+    }
+  },
   methods: {
     computedThingUid () {
       return (this.thing.bridgeUID)