bug fixes in matching algorithm for incomplete mesh (missing regions)


git-svn-id: https://geuz.org/svn/gmsh/trunk@19256 59c8cabf-10d6-4a28-b43f-3936b85956c4
git-svn-id: https://geuz.org/svn/gmsh/trunk@19257 59c8cabf-10d6-4a28-b43f-3936b85956c4
git-svn-id: https://geuz.org/svn/gmsh/trunk@19258 59c8cabf-10d6-4a28-b43f-3936b85956c4
git-svn-id: https://geuz.org/svn/gmsh/trunk@19259 59c8cabf-10d6-4a28-b43f-3936b85956c4