Fix 500 error for requests to the settings path for non-configurable plugins (#12911).

Path by Harry Garrood.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11216 e93f8b46-1217-0410-a6f0-8f06a7374b81
Plugin settings div should perhaps have 'settings' CSS class (#12910).

Patch by Harry Garrood.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11217 e93f8b46-1217-0410-a6f0-8f06a7374b81
Adjust warning message (#12251).

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11218 e93f8b46-1217-0410-a6f0-8f06a7374b81
Safer find_by_ call.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11219 e93f8b46-1217-0410-a6f0-8f06a7374b81
Don't use && return.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11220 e93f8b46-1217-0410-a6f0-8f06a7374b81
Don't use && return.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11221 e93f8b46-1217-0410-a6f0-8f06a7374b81
Code cleanup.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@11222 e93f8b46-1217-0410-a6f0-8f06a7374b81