cancel-input.diff

Index: twitvim.vim
===================================================================
--- twitvim.vim	(revision 349)
+++ twitvim.vim	(working copy)
@@ -2332,6 +2332,12 @@
     redraw
     let mesg = input("Tweet: ", a:initstr)
     call inputrestore()
+
+    if mesg == ""
+        call s:warnmsg("Your message was empty. It was not sent.")
+        return
+    endif
+
     call s:post_twitter(mesg, a:inreplyto)
 endfunction