correct error in class OneOperator_2KN_

correct error in class OneOperator_2KN_

Merge pull request FreeFem#283 from FreeFem/release-v4.13

Release v4.13

Merge pull request FreeFem#244 from FreeFem/release-v4.12

Version v4.12

Merge pull request FreeFem#224 from FreeFem/release-v4.11

Version v4.11

Merge pull request FreeFem#208 from FreeFem/release-v4.10

Version v4.10

Merge pull request FreeFem#173 from FreeFem/develop

Version 4.9

Merge pull request FreeFem#165 from FreeFem/develop

Version 4.8

Merge pull request FreeFem#158 from FreeFem/develop

Version 4.7-1

correct mistake in assert on MeshPoint of MeshL ..