RH-SSO 7.6 admin console is blank when frontendUrl is configured without a trailing slash

Issue

• After upgrading RH-SSO to 7.6, admin console doesn’t load when setting frontEndURL like below:

 ./standalone.sh -Dkeycloak.frontendUrl=http://localhost:8080/auth

or in configuration:

<spi name="hostname">
        <default-provider>default</default-provider>
        <provider name="default" enabled="true">
            <properties>
                <property name="frontendUrl" value="http://example.com/auth"/>
           ...