Fix #72850 - reading $! shouldn't SEGV if Strerror(errno) returns NULL.

This can happen on some OSes for out of range errno values. The bug was
introduced with 0097b436152452e4, which in turn fixed #61976.

Test case by Steve Peters.

1 files changed, 2 insertions, 1 deletions

diff --git a/mg.c b/mg.c
index cc01547570..06c899e35e 100644
--- a/mg.c
+++ b/mg.c
@@ -1048,7 +1048,8 @@ Perl_magic_get(pTHX_ SV *sv, MAGIC *mg)
 	else
 #endif
 	sv_setpv(sv, errno ? Strerror(errno) : "");
-	SvPOK_on(sv);	/* may have got removed during taint processing */
+	if (SvPOKp(sv))
+	    SvPOK_on(sv);    /* may have got removed during taint processing */
 	RESTORE_ERRNO;
 	}