fixed crash bug when accessing invalid group data for broken level files

Thanks to Quipyowert for finding and fixing this bug!

diff --git a/src/files.c b/src/files.c
index 45f4097f85f734dcb3645116b2bd616285a48726..49fe48569f6ddad83e5d5d78144075a60f07093d 100644 (file)
--- a/src/files.c
+++ b/src/files.c
@@ -3388,6 +3388,9 @@ static int LoadLevel_GRPX(File *file, int chunk_size, struct LevelInfo *level)
   struct ElementInfo *ei = &element_info[element];
   struct ElementGroupInfo *group = ei->group;
 
+  if (group == NULL)
+    return -1;
+
   xx_ei = *ei;         // copy element data into temporary buffer
   xx_group = *group;   // copy group data into temporary buffer