MapPreviewPage generates wicket error if Use headers for Proxy URL is enabled

Description

This looks like a regression, it was fixed in 2.14.1, now it does not work in 2.15.x

If the "Proxy Base URL" is set to "${X-Forwarded-Proto}://${X-Forwarded-Host}/geoserver"
and the "Use headers for Proxy URL" is enabled, the Layer Preview page gives the following error:

Environment

None

Assignee

Unassigned

Reporter

Gnafu

Triage

None

Fix versions

Affects versions

Components

Priority

Medium
Configure