the feed's url return an issue

[zpartakov]

Deprecated: str_getcsv(): Passing null to parameter #1 ($string) of type string is deprecated in /home/clients/sites/gulu-unige.ch/forum/vendor/flarum/core/src/Search/GambitManager.php on line 67

Fatal error: Uncaught Laminas\HttpHandlerRunner\Exception\EmitterException: Output has been emitted previously; cannot emit response in /home/clients/sites/gulu-unige.ch/forum/vendor/laminas/laminas-httphandlerrunner/src/Exception/EmitterException.php:20 
Stack trace: #0 /home/clients/sites/gulu-unige.ch/forum/vendor/laminas/laminas-httphandlerrunner/src/Emitter/SapiEmitterTrait.php(42): Laminas\HttpHandlerRunner\Exception\EmitterException::forOutputSent() 
#1 /home/clients/sites/gulu-unige.ch/forum/vendor/laminas/laminas-httphandlerrunner/src/Emitter/SapiEmitter.php(21): Laminas\HttpHandlerRunner\Emitter\SapiEmitter->assertNoPreviousOutput() 
#2 /home/clients/sites/gulu-unige.ch/forum/vendor/laminas/laminas-httphandlerrunner/src/RequestHandlerRunner.php(75): Laminas\HttpHandlerRunner\Emitter\SapiEmitter->emit(Object(Laminas\Diactoros\Response)) 
#3 /home/clients/sites/gulu-unige.ch/forum/vendor/flarum/core/src/Http/Server.php(45): Laminas\HttpHandlerRunner\RequestHandlerRunner->run() 
#4 /home/clients/sites/gulu-unige.ch/forum/public/index.php(26): Flarum\Http\Server->listen() 
#5 {main} thrown in /home/clients/sites/gulu-unige.ch/forum/vendor/laminas/laminas-httphandlerrunner/src/Exception/EmitterException.php on line 20