Fixed the JWT verifier issue

components/webapp-authenticator-framework/org.wso2.carbon.webapp.authenticator.framework/src/main/java/org/wso2/carbon/webapp/authenticator/framework/authenticator/JWTAuthenticator.java

@@ -99,7 +99,7 @@ public class JWTAuthenticator implements WebappAuthenticator {
             //Get the filesystem keystore default primary certificate
             JWSVerifier verifier = new RSASSAVerifier((RSAPublicKey) publicKey);
             //https://wso2.org/jira/browse/APIMANAGER-4504 need to change this to jwsObject.verify(verifier)
-            if (username != null && !username.isEmpty() && tenantDomain != null && !tenantDomain.isEmpty()) {
+            if (jwsObject.verify(verifier)) {
                 username = MultitenantUtils.getTenantAwareUsername(username);
                 if (tenantId == -1) {
                     log.error("tenantDomain is not valid. username : " + username + ", tenantDomain " +