Fix CVE-2017-18013:

http://bugzilla.maptools.org/show_bug.cgi?id=2770
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-18013

Patch copied from upstream source repository:

https://gitlab.com/libtiff/libtiff/commit/c6f41df7b581402dfba3c19a1e3df4454c551a01

From c6f41df7b581402dfba3c19a1e3df4454c551a01 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Sun, 31 Dec 2017 15:09:41 +0100
Subject: [PATCH] libtiff/tif_print.c: TIFFPrintDirectory(): fix null pointer
 dereference on corrupted file. Fixes
 http://bugzilla.maptools.org/show_bug.cgi?id=2770

---
 libtiff/tif_print.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libtiff/tif_print.c b/libtiff/tif_print.c
index 9959d353..8deceb2b 100644
--- a/libtiff/tif_print.c
+++ b/libtiff/tif_print.c
@@ -665,13 +665,13 @@ TIFFPrintDirectory(TIFF* tif, FILE* fd, long flags)
 #if defined(__WIN32__) && (defined(_MSC_VER) || defined(__MINGW32__))
 			fprintf(fd, "    %3lu: [%8I64u, %8I64u]\n",
 			    (unsigned long) s,
-			    (unsigned __int64) td->td_stripoffset[s],
-			    (unsigned __int64) td->td_stripbytecount[s]);
+			    td->td_stripoffset ? (unsigned __int64) td->td_stripoffset[s] : 0,
+			    td->td_stripbytecount ? (unsigned __int64) td->td_stripbytecount[s] : 0);
 #else
 			fprintf(fd, "    %3lu: [%8llu, %8llu]\n",
 			    (unsigned long) s,
-			    (unsigned long long) td->td_stripoffset[s],
-			    (unsigned long long) td->td_stripbytecount[s]);
+			    td->td_stripoffset ? (unsigned long long) td->td_stripoffset[s] : 0,
+			    td->td_stripbytecount ? (unsigned long long) td->td_stripbytecount[s] : 0);
 #endif
 	}
 }
-- 
2.16.1

