fix "can't find property of undefined" errors in mrf transparency panel

src/components/mrf_transparency_panel/mrf_transparency_panel.js

 import { mapState } from 'vuex'
+import { get } from 'lodash'
 
 const MRFTransparencyPanel = {
-  computed: mapState({
-    federationPolicy: state => state.instance.federationPolicy,
-    mrfPolicies: state => state.instance.federationPolicy.mrf_policies,
-    acceptInstances: state => state.instance.federationPolicy.mrf_simple.accept,
-    rejectInstances: state => state.instance.federationPolicy.mrf_simple.reject,
-    quarantineInstances: state => state.instance.federationPolicy.quarantined_instances,
-    ftlRemovalInstances: state => state.instance.federationPolicy.mrf_simple.federated_timeline_removal,
-    mediaNsfwInstances: state => state.instance.federationPolicy.mrf_simple.media_nsfw,
-    mediaRemovalInstances: state => state.instance.federationPolicy.mrf_simple.media_removal
-  })
+  computed: {
+    ...mapState({
+      federationPolicy: state => get(state, 'instance.federationPolicy'),
+      mrfPolicies: state => get(state, 'instance.federationPolicy.mrf_policies', []),
+      quarantineInstances: state => get(state, 'instance.federationPolicy.quarantined_instances', []),
+      acceptInstances: state => get(state, 'instance.federationPolicy.mrf_simple.accept', []),
+      rejectInstances: state => get(state, 'instance.federationPolicy.mrf_simple.reject', []),
+      ftlRemovalInstances: state => get(state, 'instance.federationPolicy.mrf_simple.federated_timeline_removal', []),
+      mediaNsfwInstances: state => get(state, 'instance.federationPolicy.mrf_simple.media_nsfw', []),
+      mediaRemovalInstances: state => get(state, 'instance.federationPolicy.mrf_simple.media_removal', [])
+    }),
+    hasInstanceSpecificPolicies () {
+      return this.quarantineInstances.length ||
+        this.acceptInstances.length ||
+        this.rejectInstances.length ||
+        this.ftlRemovalInstances.length ||
+        this.mediaNsfwInstances.length ||
+        this.mediaRemovalInstances.length
+    }
+  }
 }
 
 export default MRFTransparencyPanel

src/components/mrf_transparency_panel/mrf_transparency_panel.vue

@@ -22,7 +22,9 @@
             />
           </ul>
 
-          <h2>{{ $t("about.mrf_policy_simple") }}</h2>
+          <h2 v-if="hasInstanceSpecificPolicies">
+            {{ $t("about.mrf_policy_simple") }}
+          </h2>
 
           <div v-if="acceptInstances.length">
             <h4>{{ $t("about.mrf_policy_simple_accept") }}</h4>