libtiff: Check return value of _TIFFCreateAnonField().

From 818fb8ce881cf839fbc710f6690aadb992aa0f9e Mon Sep 17 00:00:00 2001
From: Su_Laus <[EMAIL REDACTED]>
Date: Fri, 1 Dec 2023 20:12:25 +0100
Subject: [PATCH] Check return value of _TIFFCreateAnonField().

Fixes #624
---
 libtiff/tif_dirinfo.c |  2 +-
 libtiff/tif_dirread.c | 16 ++++++----------
 2 files changed, 7 insertions(+), 11 deletions(-)

diff --git a/libtiff/tif_dirinfo.c b/libtiff/tif_dirinfo.c
index bff7592a..2338ca21 100644
--- a/libtiff/tif_dirinfo.c
+++ b/libtiff/tif_dirinfo.c
@@ -887,7 +887,7 @@ const TIFFField *_TIFFFindOrRegisterField(TIFF *tif, uint32_t tag,
     if (fld == NULL)
     {
         fld = _TIFFCreateAnonField(tif, tag, dt);
-        if (!_TIFFMergeFields(tif, fld, 1))
+        if (fld == NULL || !_TIFFMergeFields(tif, fld, 1))
             return NULL;
     }
 
diff --git a/libtiff/tif_dirread.c b/libtiff/tif_dirread.c
index c7969414..242912f3 100644
--- a/libtiff/tif_dirread.c
+++ b/libtiff/tif_dirread.c
@@ -4278,11 +4278,9 @@ int TIFFReadDirectory(TIFF *tif)
                                 dp->tdir_tag, dp->tdir_tag);
                 /* the following knowingly leaks the
                    anonymous field structure */
-                if (!_TIFFMergeFields(
-                        tif,
-                        _TIFFCreateAnonField(tif, dp->tdir_tag,
-                                             (TIFFDataType)dp->tdir_type),
-                        1))
+                const TIFFField *fld = _TIFFCreateAnonField(
+                    tif, dp->tdir_tag, (TIFFDataType)dp->tdir_type);
+                if (fld == NULL || !_TIFFMergeFields(tif, fld, 1))
                 {
                     TIFFWarningExtR(
                         tif, module,
@@ -5156,11 +5154,9 @@ int TIFFReadCustomDirectory(TIFF *tif, toff_t diroff,
                             "Unknown field with tag %" PRIu16 " (0x%" PRIx16
                             ") encountered",
                             dp->tdir_tag, dp->tdir_tag);
-            if (!_TIFFMergeFields(
-                    tif,
-                    _TIFFCreateAnonField(tif, dp->tdir_tag,
-                                         (TIFFDataType)dp->tdir_type),
-                    1))
+            const TIFFField *fld = _TIFFCreateAnonField(
+                tif, dp->tdir_tag, (TIFFDataType)dp->tdir_type);
+            if (fld == NULL || !_TIFFMergeFields(tif, fld, 1))
             {
                 TIFFWarningExtR(tif, module,
                                 "Registering anonymous field with tag %" PRIu16