Readded Delete Message Button for own user and outBox, and ensured delete message is avaliable for all roles above admin

Author: KshitizSareen

src/action-sheets/index.js

@@ -693,6 +693,7 @@ export const constructMessageActionButtons = (args: {|
   const { backgroundData, message, narrow, canStartQuoteAndReply } = args;
   const { ownUser, flags } = backgroundData;
   const buttons = [];
+  let deleteMessageAdded = false;
 
   if (message.isOutbox === true) {
     buttons.push(copyToClipboard);
@@ -729,6 +730,15 @@ export const constructMessageActionButtons = (args: {|
   if (message.sender_id === ownUser.user_id && messageNotDeleted(message)) {
     // TODO(#2793): Don't show if message isn't deletable.
     buttons.push(deleteMessage);
+    deleteMessageAdded = true;
+  }
+  if (
+    ownUser.role !== undefined
+    && roleIsAtLeast(ownUser.role, Role.Admin)
+    && messageNotDeleted(message)
+    && !deleteMessageAdded
+  ) {
+    buttons.push(deleteMessage);
   }
   if (
     // When do we offer "Mark as unread from here"?  This logic parallels

src/chat/ChatScreen.js

@@ -164,7 +164,7 @@ export default function ChatScreen(props: Props): Node {
           () => undefined,
         );
 
-        if ((content !== undefined && content !== '') || (topic !== undefined && topic !== '')) {
+        if (content !== undefined || topic !== undefined) {
           api.updateMessage(auth, editMessage.id, { content, subject: topic }).catch(error => {
             showErrorAlert(_('Failed to edit message'), error.message);
           });

src/compose/ComposeBox.js

@@ -521,7 +521,7 @@ const ComposeBox: React$AbstractComponent<Props, ImperativeHandle> = forwardRef(
       result.push('mandatory-topic-empty');
     }
 
-    if (messageInputValue.trim().length === 0) {
+    if (messageInputValue.trim().length === 0 && !isEditing) {
       result.push('message-empty');
     }
 
@@ -535,11 +535,12 @@ const ComposeBox: React$AbstractComponent<Props, ImperativeHandle> = forwardRef(
 
     return result;
   }, [
+    messageInputState,
     destinationNarrow,
     mandatoryTopics,
+    isEditing,
     numUploading,
     anyQuoteAndReplyInProgress,
-    messageInputState,
   ]);
 
   const submitButtonDisabled = validationErrors.length > 0;