Added null checking to prevent bot from crashing if user name, text o…

…r channel cannot be determined.

examples/simple_reverse.coffee

@@ -53,18 +53,27 @@ slack.on 'message', (message) ->
   channelName = if channel.is_channel then '#' else ''
   channelName += channel.name
 
+  userName = if user?.name? then "@#{user.name}" else "UNKNOWN_USER"
+
   console.log """
-    Received: #{type} #{channelName} @#{user.name} #{ts} "#{text}"
+    Received: #{type} #{channelName} #{userName} #{ts} "#{text}"
   """
 
   # Respond to messages with the reverse of the text received.
 
-  if type is 'message'
+  if type is 'message' and text? and channel?
     response = text.split('').reverse().join('')
     channel.send response
     console.log """
       @#{slack.self.name} responded with "#{response}"
     """
+  else
+    textError = if not text? then 'text was undefined.' else ''
+    channelError = if not channel? then 'channel was undefined.' else ''
+
+    console.log """
+      @#{slack.self.name} could not respond. #{textError} #{channelError}
+    """
 
 
 slack.on 'error', (error) ->