removed unneeded cache

lib/compass/sprite_importer.rb

@@ -56,12 +56,10 @@ module Compass
     end
     
     def self.path_and_name(uri)
-      Compass.quick_cache "Sprite_map_name:#{uri}", 5 do
       if uri =~ SPRITE_IMPORTER_REGEX
         [$1, $3]
       else
-          [nil, nil]
-        end
+        raise Compass::Error "invalid sprite path"
       end
     end