Fix crash in WorkingMessage.saveAsMms

A set of steps will correctly cause the working message to get marked
as discarded. However, when restarting, the discarded working message
was not replaced with a good working message. Bug 1866477

Change-Id: I4b42402e3d539df2792b20fa5c3a2f4567085f08

src/com/android/mms/ui/ComposeMessageActivity.java

@@ -1888,6 +1888,10 @@ protected void onRestart() {
                 mWorkingMessage.unDiscard();    // it was discarded in onStop().
             } else if (isRecipientsEditorVisible()) {
                 goToConversationList();
+            } else {
+                loadDraft();
+                mWorkingMessage.setConversation(mConversation);
+                mAttachmentEditor.update(mWorkingMessage);
             }
         }
     }