Always clear message drafts after sending a text message.

// FREEBIE

Signal/src/ViewControllers/MessagesViewController.m

@@ -1509,6 +1509,7 @@ typedef enum : NSUInteger {
         {
             [self toggleDefaultKeyboard];
         }
+        [self clearDraft];
         [self finishSendingMessage];
     }
 }
@@ -3354,6 +3355,14 @@ typedef enum : NSUInteger {
     }
 }
 
+- (void)clearDraft
+{
+    __block TSThread *thread = _thread;
+    [self.editingDatabaseConnection asyncReadWriteWithBlock:^(YapDatabaseReadWriteTransaction *transaction) {
+        [thread setDraft:@"" transaction:transaction];
+    }];
+}
+
 #pragma mark Unread Badge
 
 - (void)updateBackButtonUnreadCount