Starting with Geoserver 2.11.3 the options "Guess Parameters from SQL" and "Add new Parameter" in an SQL View are failing with an exception shown below.
Workflow to reproduce the issue:
clean Geoserver installation (War in Tomcat), no external data directory set
added new workspace (checked as default workspace)
added new POSTGIS DataSource
create SQL View
click "Add new Parameter" or define SQL with %PARAMNAME% Placeholder and click "Guess Parameters from SQL"
Same Workflow works in versions before 2.11.3.
Once the view is created (e.g. use an older version of Geoserver to create the view and the upgrade geoserver) it can be rendered by the afflicted versions. So it seams its just a problem during creation in the UI.
clean geoserver with test files included, no external data directory
added workspace & Postgis Datasource