More fixes for 258060

Fixes a bug which could cause a crash when the update item is chosen by the delegate from the appcast. Thanks, Christiaan Hofman.

SUBasicUpdateDriver.m

@@ -79,22 +79,24 @@ - (void)appcastDidFinishLoading:(SUAppcast *)ac
 {
 	if ([[updater delegate] respondsToSelector:@selector(updater:didFinishLoadingAppcast:)])
 		[[updater delegate] updater:updater didFinishLoadingAppcast:ac];
-		
+    
+    SUAppcastItem *item = nil;
+    
 	// Now we have to find the best valid update in the appcast.
 	if ([[updater delegate] respondsToSelector:@selector(bestValidUpdateInAppcast:forUpdater:)]) // Does the delegate want to handle it?
 	{
-		updateItem = [[updater delegate] bestValidUpdateInAppcast:ac forUpdater:updater];
+		item = [[updater delegate] bestValidUpdateInAppcast:ac forUpdater:updater];
 	}
 	else // If not, we'll take care of it ourselves.
 	{
 		// Find the first update we can actually use.
 		NSEnumerator *updateEnumerator = [[ac items] objectEnumerator];
 		do {
-			updateItem = [updateEnumerator nextObject];
-		} while (updateItem && ![self hostSupportsItem:updateItem]);
-		
-		[updateItem retain];
+			item = [updateEnumerator nextObject];
+		} while (item && ![self hostSupportsItem:item]);
 	}
+    
+    updateItem = [item retain];
 	CFRelease(ac); // Remember that we're explicitly managing the memory of the appcast.
 	if (updateItem == nil) { [self didNotFindUpdate]; return; }