Fix crash when closing a repository while the commits are still being loaded

Author: ksuther

Classes/Controllers/PBViewController.h

@@ -13,11 +13,11 @@
 
 @interface PBViewController : NSViewController {
 	// FIXME: these ivars must go, but most controller out there access it directly, so, not today
-	PBGitRepository *repository;
+	__weak PBGitRepository *repository;
 	__weak PBGitWindowController *superController;
 }
 
-@property (nonatomic, strong, readonly) PBGitRepository *repository;
+@property (nonatomic, weak, readonly) PBGitRepository *repository;
 @property (weak, readonly) PBGitWindowController *windowController;
 @property (copy) NSString *status;
 @property (assign) BOOL isBusy;

Classes/Controllers/PBViewController.m

@@ -36,8 +36,6 @@ - (void)closeView
 	[self unbind:@"repository"];
 	if (_hasViewLoaded)
 		[[self view] removeFromSuperview];	// remove the current view
-	repository = nil;
-	superController = nil;
 }
 
 - (void)awakeFromNib