templatekw: apply manifest template only if ctx.manifestnode() exists This will prevent crash by "hg log -r 'wdir()' -Tdefault". We could use the pseudo ff... hash introduced by 183965a00c76, but it isn't proven idea yet. For now, I want to make "hg log" just works in order to test 'wdir()' revset. Note that unlike its name, "{manifest}" is not a list of files in that revision, but a pair of (manifestrev, manifestnode).