Merged revisions 221200 via svnmerge from

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

........
  r221200 | tilghman | 2009-09-30 11:55:21 -0500 (Wed, 30 Sep 2009) | 7 lines
  
  Avoid a potential NULL dereference.
  (closes issue #15865)
   Reported by: kobaz
   Patches: 
         20090915__issue15865.diff.txt uploaded by tilghman (license 14)
   Tested by: kobaz
........


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@221201 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/channel.c

@@ -2977,9 +2977,9 @@ static void send_dtmf_event(const struct ast_channel *chan, const char *directio
 
 static void ast_read_generator_actions(struct ast_channel *chan, struct ast_frame *f)
 {
-	if (chan->generatordata &&  !ast_internal_timing_enabled(chan)) {
+	if (chan->generator && chan->generator->generate && chan->generatordata &&  !ast_internal_timing_enabled(chan)) {
 		void *tmp = chan->generatordata;
-		int (*generate)(struct ast_channel *chan, void *tmp, int datalen, int samples) = NULL;
+		int (*generate)(struct ast_channel *chan, void *tmp, int datalen, int samples) = chan->generator->generate;
 		int res;
 		int samples;
 
@@ -2998,9 +2998,6 @@ static void ast_read_generator_actions(struct ast_channel *chan, struct ast_fram
 			samples = f->samples;
 		}
 		
-		if (chan->generator->generate) {
-			generate = chan->generator->generate;
-		}
 		/* This unlock is here based on two assumptions that hold true at this point in the
 		 * code. 1) this function is only called from within __ast_read() and 2) all generators
 		 * call ast_write() in their generate callback.