revset: ensure we have loaded phases data in '_notpublic()'

If we are the very first rev access (or if the phase cache just got
invalidated) the phasesets will be None even if we support the native
computation. So we explicitly trigger a computation if needed.

This was not an issue before because requesting any phase information
would have triggered such computation.

mercurial/revset.py

@@ -1513,6 +1513,7 b' def present(repo, subset, x):'
 # for internal use
 def _notpublic(repo, subset, x):
     getargs(x, 0, 0, "_notpublic takes no arguments")
+    repo._phasecache.loadphaserevs(repo) # ensure phase's sets are loaded
     if repo._phasecache._phasesets:
         s = set()
         for u in repo._phasecache._phasesets[1:]: