Sending an email breaks with NPE exception

Configuring the server
1

I’m trying to send a custom email like this

    EmailTemplateProvider emailProvider = context.getSession().getProvider(EmailTemplateProvider.class);
    emailProvider.send(subject, emailTemplate, new HashMap<>());

But this breaks with the next exception

org.keycloak.email.EmailException: Failed to template email
at org.keycloak.keycloak-services@15.0.2//org.keycloak.email.freemarker.FreeMarkerEmailTemplateProvider.processTemplate(FreeMarkerEmailTemplateProvider.java:233)
at org.keycloak.keycloak-services@15.0.2//org.keycloak.email.freemarker.FreeMarkerEmailTemplateProvider.send(FreeMarkerEmailTemplateProvider.java:244)
...
Caused by: java.lang.NullPointerException 
at org.keycloak.keycloak-services@15.0.2//org.keycloak.email.freemarker.FreeMarkerEmailTemplateProvider.processTemplate(FreeMarkerEmailTemplateProvider.java:212)

The said line (212 in processTemplate method) is

 rb.putAll(realm.getRealmLocalizationTextsByLocale(locale.toLanguageTag()));

it’s not really clear from the exception why this actually happens

Do I need to configure the provider manually with the realm, locale etc.?