Bug Fix: Add some safety checks to URL handlers

A few places could have used nil checks, but there shouldn't be anything
passing nil URLs to these. Well, just in case, at least it won't lead to
crashes or something...

Signed-off-by: Christopher Snowhill <kode54@gmail.com>

Audio/Chain/BufferChain.m

@@ -52,6 +52,10 @@
 }
 
 - (BOOL)open:(NSURL *)url withOutputFormat:(AudioStreamBasicDescription)outputFormat withUserInfo:(id)userInfo withRGInfo:(NSDictionary *)rgi {
+	if(!url) {
+		DLog(@"Player attempted to play invalid file...");
+		return NO;
+	}
 	[self setStreamURL:url];
 	[self setUserInfo:userInfo];
 

Playlist/PlaylistLoader.m

@@ -1112,6 +1112,7 @@ NSURL *_Nullable urlForPath(NSString *_Nullable path);
 }
 
 - (NSArray *)addURL:(NSURL *)url {
+	if(!url) return [NSArray array];
 	return [self insertURLs:@[url] atIndex:(int)[[playlistController content] count] sort:NO];
 }
 

Utils/SandboxBroker.m

@@ -420,6 +420,7 @@ static inline void dispatch_async_reentrant(dispatch_queue_t queue, dispatch_blo
 }
 
 - (const void *)beginFolderAccess:(NSURL *)fileUrl {
+	if(!fileUrl) return NULL;
 	NSURL *folderUrl = [SandboxBroker urlWithoutFragment:fileUrl];
 	if(![folderUrl isFileURL]) return NULL;