Please, do not commit spacing modification in a bug, it will be horrible to merge. 
To keep your modifiication without the space, you can do:
$ git diff --no-color -w branches/rudder/2.4 --  rudder-web/src/main/scala/bootstrap/liftweb/AppConfig.scala > appconfig.patch
$ git co branches/rudder/2.4 --  rudder-web/src/main/scala/bootstrap/liftweb/AppConfig.scala
$ patch -p1 < appconfig.patch