libtiff: Merge branch 'mymaster1' into 'master'

From 8c0859a80444c90b8dfb862a9f16de74e16f0a9e Mon Sep 17 00:00:00 2001
From: xiaoxiaoafeifei <[EMAIL REDACTED]>
Date: Fri, 21 Apr 2023 13:01:34 +0000
Subject: [PATCH] countInkNamesString(): fix `UndefinedBehaviorSanitizer`:
 applying zero offset to null pointer

---
 libtiff/tif_dir.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/libtiff/tif_dir.c b/libtiff/tif_dir.c
index 3d57341f..c3a7a418 100644
--- a/libtiff/tif_dir.c
+++ b/libtiff/tif_dir.c
@@ -192,11 +192,11 @@ static int setExtraSamples(TIFF *tif, va_list ap, uint32_t *v)
 static uint16_t countInkNamesString(TIFF *tif, uint32_t slen, const char *s)
 {
     uint16_t i = 0;
-    const char *ep = s + slen;
-    const char *cp = s;
 
     if (slen > 0)
     {
+        const char *ep = s + slen;
+        const char *cp = s;
         do
         {
             for (; cp < ep && *cp != '\0'; cp++)