(svn r17302) [0.7] -Backport from trunk:

- Fix: [NoAI] Reloading an AI started a new AI in the first available company slot causing other AIs to be started [FS#3153] (r17298)
- Fix: Crash after upgrading base graphics set when opening the game options menu and you were using the upgraded set [FS#3147] (r17291)
- Fix: [Squirrel] Stack was not always cleared properly with tail recursion (r17284)
- Fix: [Squirrel] Calling a function that has default parameters with not enough parameters can cause a crash (r17273)
- Change: Mention the MD5 checksum of the original NewGRF in the "saveload failed horribly"-error message and make it more clear that the filename is of the current NewGRF [FS#3139] (r17267)

src/gfxinit.cpp

@@ -493,6 +493,11 @@ bool OBGFileScanner::AddFile(const char *filename, size_t basepath_length)
 				/* don't allow recursive delete of all remaining items */
 				duplicate->next = NULL;
 
+				/* If the duplicate set is currently used (due to rescanning this can happen)
+				 * update the currently used set to the new one. This will 'lie' about the
+				 * version number until a new game is started which isn't a big problem */
+				if (_used_graphics_set == duplicate) _used_graphics_set = graphics;
+
 				DEBUG(grf, 1, "Removing %s (%i) as base graphics set (duplicate)", duplicate->name, duplicate->version);
 				delete duplicate;
 				ret = true;