Error 500: Laravel and Angular 4 Invalid header name type; expected string; received integer

I have a backend using laravel 5.4 and a frontend with Angular 4, there's a error that I couldnt find, I dont know if is a backend or frontend problem.

When I want to get a list of 'convocatorias' is through this route:

http://localhost:8000//api/administracion/configuraciones/convocatorias/?cantidad=6&page=1 => It is working good on postman

But, when I click on button 'Buscar' on frontend there's a random 500 error :

.

I print the name variable on the HeaderSecurity.php assertValidName function and here are the results:

With error: hostconnectionacceptoriginauthorizationuser-agent0

Without error: hostconnectionacceptoriginauthorizationuser-agentcontent-typerefereraccept-encodingaccept-language

Is an Angular problem or is Laravel? Please explain the correct way to resolve this issue.