better errors if meterp file is missing

git-svn-id: file:///home/svn/framework3/trunk@4313 4d416f70-5f16-0410-b530-b9f4589650da

lib/rex/post/meterpreter/ui/console/command_dispatcher/core.rb

@@ -424,6 +424,9 @@ protected
 				klass = CommDispatcher.const_get(diff[0])
 
 				CommDispatcher.set_hash(path, klass)
+			else
+				print_error("Failed to load client script file: #{clirb}")
+				return false
 			end
 		end