Following the head refactoring, the Newz doesn't clear the SvPVX

So PL_mess_sv contained an uninitialised value.

p4raw-id: //depot/perl@24657

1 files changed, 1 insertions, 0 deletions

diff --git a/util.c b/util.c
index f80eb63c9b..8b683a7453 100644
--- a/util.c
+++ b/util.c
@@ -875,6 +875,7 @@ S_mess_alloc(pTHX)
     Newz(905, any, 1, XPVMG);
     SvFLAGS(sv) = SVt_PVMG;
     SvANY(sv) = (void*)any;
+    SvPV_set(sv, 0);
     SvREFCNT(sv) = 1 << 30; /* practically infinite */
     PL_mess_sv = sv;
     return sv;