Check for malloc fail before setting buffer

Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

src/dvd_reader.c

@@ -1445,7 +1445,6 @@ int DVDISOVolumeInfo( dvd_reader_t *dvd,
   }
 
   buffer_base = malloc( DVD_VIDEO_LB_LEN + 2048 );
-  buffer = (unsigned char *)(((uintptr_t)buffer_base & ~((uintptr_t)2047)) + 2048);
 
   if( buffer_base == NULL ) {
     fprintf( stderr, "libdvdread: DVDISOVolumeInfo, failed to "
@@ -1453,6 +1452,8 @@ int DVDISOVolumeInfo( dvd_reader_t *dvd,
     return -1;
   }
 
+  buffer = (unsigned char *)(((uintptr_t)buffer_base & ~((uintptr_t)2047)) + 2048);
+
   ret = InternalUDFReadBlocksRaw( dvd, 16, 1, buffer, 0 );
   if( ret != 1 ) {
     fprintf( stderr, "libdvdread: DVDISOVolumeInfo, failed to "