Return a proper error when starting the watcher when there's nothing to compile.

Closes GH-119

lib/compass/commands/update_project.rb

@@ -29,12 +29,15 @@ module Compass
 
       def perform
         compiler = new_compiler_instance
+        check_for_sass_files!(compiler)
+        compiler.run
+      end
+
+      def check_for_sass_files!(compiler)
         if compiler.sass_files.empty? && !dry_run?
           message = "Nothing to compile. If you're trying to start a new project, you have left off the directory argument.\n"
           message << "Run \"compass -h\" to get help."
           raise Compass::Error, message
-        else
-          compiler.run
         end
       end
 

lib/compass/commands/watch_project.rb

@@ -36,6 +36,7 @@ module Compass
           exit 0
         end
 
+        check_for_sass_files!(new_compiler_instance)
         recompile
 
         begin