engine: fix crash when reading GoldSrc hashpaks

engine/common/hpak.c

@@ -702,11 +702,13 @@ qboolean HPAK_GetDataPointer( const char *filename, resource_t *pResource, byte
 	{
 		entry = &directory.entries[i];
 
-		if( !memcmp( entry->resource.rgucMD5_hash, pResource->rgucMD5_hash, 16 ))
+		if( entry->filepos > 0 &&
+			entry->disksize > 0 &&
+			!memcmp( entry->resource.rgucMD5_hash, pResource->rgucMD5_hash, 16 ))
 		{
 			FS_Seek( f, entry->filepos, SEEK_SET );
 
-			if( buffer && entry->disksize > 0 )
+			if( buffer )
 			{
 				tmpbuf = Z_Malloc( entry->disksize );
 				FS_Read( f, tmpbuf, entry->disksize );