DEPRECATED USE in libdispatch client on Mojave and Xcode 10.1

This error constantly appearing in the system.log:

DEPRECATED USE in libdispatch client: dispatch source activated with no event handler set; set a breakpoint on _dispatch_bug_deprecated to debug

The code in question is given bellow:

dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
    [self doItInTheBackground];
    dispatch_async(dispatch_get_main_queue(), ^{
        [self.loadingSpinner stopAnimation:self];
        [self.loadingPanel close];
    });
});

EDIT:

Any program using GCD library seems to be getting this error, including systems apps like Terminal, Console, AppStore, etc.

EDIT 2:

As of 10.14.4, I can see several other messages as well, e.g.:

DEPRECATED USE in libdispatch client: Setting timer interval to 0 requests a 1ns timer, did you mean FOREVER (a one-shot timer)?; set a breakpoint on _dispatch_bug_deprecated to debug

And

BUG in libdispatch client: mach_recv, monitored resource vanished before the source cancel handler was invoked { 0xXXXXXXXXXXXX[source], ident: XX / 0xXX, handler: 0xXXXXXXXXXXXX }