Fixed post draft selectors returning null (#932)

app/components/file_upload_preview/index.js

@@ -21,6 +21,10 @@ const checkForFileUploadingInChannel = createSelector(
         return state.views.channel.drafts[channelId];
     },
     (draft) => {
+        if (!draft || !draft.files) {
+            return false;
+        }
+
         return draft.files.some((f) => f.loading);
     }
 );

app/selectors/views.js

@@ -1,7 +1,15 @@
+// Copyright (c) 2017-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
 import {createSelector} from 'reselect';
 
 import {getCurrentChannel} from 'mattermost-redux/selectors/entities/channels';
 
+const emptyDraft = {
+    draft: '',
+    files: []
+};
+
 function getChannelDrafts(state) {
     return state.views.channel.drafts;
 }
@@ -13,11 +21,15 @@ function getThreadDrafts(state) {
 export const getCurrentChannelDraft = createSelector(
     getChannelDrafts,
     getCurrentChannel,
-    (drafts, currentChannel) => drafts[currentChannel.id]
+    (drafts, currentChannel) => {
+        return drafts[currentChannel.id] || emptyDraft;
+    }
 );
 
 export const getThreadDraft = createSelector(
     getThreadDrafts,
     (state, rootId) => rootId,
-    (drafts, rootId) => drafts[rootId]
+    (drafts, rootId) => {
+        return drafts[rootId] || emptyDraft;
+    }
 );