Merged revisions 276652 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.4

........
  r276652 | jpeeler | 2010-07-15 08:48:58 -0500 (Thu, 15 Jul 2010) | 2 lines
  
  In a perfect world, the frame source would never be NULL. In the meantime, don't crash when it is.
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@276653 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/channel.c

@@ -4553,7 +4553,7 @@ int ast_write(struct ast_channel *chan, struct ast_frame *fr)
 		res = 0;	/* XXX explain, why 0 ? */
 		goto done;
 	}
-	if (chan->generatordata && strcasecmp(fr->src, "ast_prod")) {
+	if (chan->generatordata && (!fr->src || strcasecmp(fr->src, "ast_prod"))) {
 		if (ast_test_flag(chan, AST_FLAG_WRITE_INT)) {
 				ast_deactivate_generator(chan);
 		} else {