Exception throws when ErrorPage or IndexPage properties are not configured in the configuration file

**Description:**
Below exception throws when ErrorPage property is not configured in the configuration file at the logout
java.lang.IllegalArgumentException: Path [samlsso?SAML2.HTTPBinding=HTTP-POST] does not start with a "/" character

**Suggested Labels:**

SAML,SLO,Tomcat
**Suggested Assignees:**

**Affected Product Version:**
sgardio-java-oidc-sdk release version 0.1.16
**OS, DB, other environment details and versions:**
WSO2 IAM 5.10.0, Tomcat 9.0

**Steps to reproduce:**

1. Setup asgardio tomcat sample app : https://github.com/asgardio/asgardio-tomcat-saml-agent/tree/master/io.asgardio.tomcat.saml.agent.sample by using asgardio-java-oidc-sdk release version 0.1.16
2. Remove below properties from the sample-app.properties
IndexPage=/sample-app/index.html
ErrorPage=/error.jsp
3. Check the logout flow

Start with the asgardio-tomcat-saml-agent sample app and its sample-app.properties, removing IndexPage and ErrorPage as described. Reproduce the logout flow and trace the resulting IllegalArgumentException for the samlsso path. Done means logout completes without the path error when those properties are absent.

Written by the indexing model from the issue text.