Merged revisions 318921 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.8

........
  r318921 | bbryant | 2011-05-13 14:09:34 -0400 (Fri, 13 May 2011) | 8 lines
  
  Fixes a segmentation fault in dynamic hints when a channel technology isn't
  loaded for a hint.
  
  (closes issue #18495)
  Reported by: bertrand
  Tested by: bertrand
........


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@318922 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/channel.c

@@ -3882,7 +3882,7 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio)
 			}
 			/* Clear the exception flag */
 			ast_clear_flag(chan, AST_FLAG_EXCEPTION);
-		} else if (chan->tech->read)
+		} else if (chan->tech && chan->tech->read)
 			f = chan->tech->read(chan);
 		else
 			ast_log(LOG_WARNING, "No read routine on channel %s\n", chan->name);