Unload all keys of all pages before deleting them

(ported from H-uru/Plasma@04d0ac94ea25fc937931b8f4f546220ddf1cc27c)

Sources/Plasma/PubUtilLib/plResMgr/plResManager.cpp

@@ -219,14 +219,20 @@ void plResManager::IShutdown()
 	// Shut down the registry (finally!)
 	ILockPages();
 
-	PageSet::const_iterator it;
+	// Unload all keys before actually deleting the pages.
-	for (it = fAllPages.begin(); it != fAllPages.end(); it++)
+	// When a key's refcount drops to zero, IKeyUnreffed looks up the key's page.
+	// If the page is already deleted at that point, this causes a use after free and potential crash.
+	for (PageSet::const_iterator it = fAllPages.begin(); it != fAllPages.end(); it++) {
+		(*it)->UnloadKeys();
+	}
+	fLoadedPages.clear();
+	fLastFoundPage = nil;
+	for (PageSet::const_iterator it = fAllPages.begin(); it != fAllPages.end(); it++) {
 		delete *it;
+	}
 	fAllPages.clear();
-	fLoadedPages.clear();
 
 	IUnlockPages();
-	fLastFoundPage = nil;
 
 	// Now, kill off the Dispatcher
 	hsRefCnt_SafeUnRef(fDispatch);