Disabled mapping from ideal element when calculatin Jacobian, introduced in r19425

git-svn-id: https://geuz.org/svn/gmsh/trunk@19528 59c8cabf-10d6-4a28-b43f-3936b85956c4
git-svn-id: https://geuz.org/svn/gmsh/trunk@19529 59c8cabf-10d6-4a28-b43f-3936b85956c4