macosx: fix possible SPMediaKeyTap crash

Adding nil to an NSArray would make it raise an
NSInvalidArgumentException which in turn leads to an abort in
dispatch_once:
  https://github.com/apple-oss-distributions/libdispatch/blob/55c3a68e9ec47f1c1d5bb9909404ce5f0351edef/src/object.m#L557

Fix #27487

modules/gui/macosx/imported/SPMediaKeyTap/SPMediaKeyTap.m

@@ -173,8 +173,13 @@ + (NSArray*)mediaKeyUserBundleIdentifiers
     static NSArray *bundleIdentifiers;
     static dispatch_once_t onceToken;
     dispatch_once(&onceToken, ^{
+        NSString *ourIdentifier = [[NSBundle mainBundle] bundleIdentifier];
+        if (ourIdentifier == nil) {
+            NSLog(@"SPMediaKeyTap: Bundle identifier unexpectedly nil, falling back to org.videolan.vlc");
+            ourIdentifier = @"org.videolan.vlc";
+        }
         bundleIdentifiers = @[
-            [[NSBundle mainBundle] bundleIdentifier], // your app
+            ourIdentifier, // your app
             @"com.spotify.client",
             @"com.apple.iTunes",
             @"com.apple.Music",