Due to SECURITY-624, a bug was revealed in ToolsDirective/config.jelly. The initial correction proposed to
JENKINS-51872, was to add the h variable to two blocks.
The first one, to ToolsDirective/config.jelly, was legitimate but the second one (in symbol-hetero-list.jelly) is not useful since the internal block use a layout (l:ajax in this case) and thus, the h variable is defined there.
Proposition: remove the non-required correction in symbol-hetero-list.jelly and use l:ajax in ToolsDirective/config.jelly.