Filter out non-convergence in PKF

Upon non-convergence, we seem to save the invalid results from the last iteration. See https://forum.dynare.org/t/occbin-estimation-bk-conditions-are-not-satisfied/20721/20

added bug occbin labels

yes, this is not correctly filtered out!

mentioned in commit JohannesPfeifer/dynare@4f35e002

mentioned in merge request !2100 (merged)

mentioned in commit JohannesPfeifer/dynare@5e3d35ea

mentioned in commit JohannesPfeifer/dynare@4d603fb3

mentioned in commit 3184db12

closed with commit 4d603fb3

closed with merge request !2100 (merged)

mentioned in commit JohannesPfeifer/dynare@16ffe728

mentioned in commit JohannesPfeifer/dynare@c1ed5d0f