8380078: Update GIFlib to 6.1.2

Backport-of: 76e7c9e

Author: GoeLin

src/java.desktop/share/legal/giflib.md

@@ -1,4 +1,4 @@
-## GIFLIB v6.1.1
+## GIFLIB v6.1.2
 
 ### GIFLIB License
 ```

src/java.desktop/share/native/libsplashscreen/giflib/gif_lib.h

@@ -39,7 +39,7 @@ extern "C" {
 
 #define GIFLIB_MAJOR 6
 #define GIFLIB_MINOR 1
-#define GIFLIB_RELEASE 1
+#define GIFLIB_RELEASE 2
 
 #define GIF_ERROR 0
 #define GIF_OK 1

src/java.desktop/share/native/libsplashscreen/giflib/gifalloc.c

@@ -373,6 +373,14 @@ SavedImage *GifMakeSavedImage(GifFileType *GifFile,
                          * aliasing problems.
                          */
 
+                        /* Null out aliased pointers before any allocations
+                         * so that FreeLastSavedImage won't free CopyFrom's
+                         * data if an allocation fails partway through. */
+                        sp->ImageDesc.ColorMap = NULL;
+                        sp->RasterBits = NULL;
+                        sp->ExtensionBlocks = NULL;
+                        sp->ExtensionBlockCount = 0;
+
                         /* first, the local color map */
                         if (CopyFrom->ImageDesc.ColorMap != NULL) {
                                 sp->ImageDesc.ColorMap = GifMakeMapObject(