Fixed the following bug. When dialing *99 it produces this error.

2013-02-21 18:39:28.016638 [ERR] mod_lua.cpp:198 ...app/voicemail/resources/functions/record_message.lua:39: bad argument #1 to 'len' (string expected, got nil)

includes/install/scripts/app/voicemail/resources/functions/record_message.lua

@@ -36,6 +36,7 @@
 			end
 
 		--direct dial
+			if (dtmf_digits ~= nil) then
 				if (string.len(dtmf_digits) > 0) then
 					if (session:ready()) then
 						if (direct_dial["enabled"] == "true") then
@@ -60,6 +61,7 @@
 						end
 					end
 				end
+			end
 
 		--play the beep
 			dtmf_digits = '';