ocaml_402: don't report some warnings on erroneous expressions
ocaml_402: don't report some warnings on erroneous expressions

chriskonstad/merlin,dra27/merlin,dra27/merlin,ocaml/merlin,fxfactorial/merlin,fxfactorial/merlin,ocaml/merlin,rgrinberg/merlin,the-lambda-church/merlin,chambart/merlin,chambart/merlin,rgrinberg/merlin,fxfactorial/merlin,chriskonstad/merlin,rgrinberg/merlin,fxfactorial/merlin,ocaml/merlin,dra27/merlin,ocaml/merlin,chambart/merlin,rgrinberg/merlin,the-lambda-church/merlin,dra27/merlin,the-lambda-church/merlin,chambart/merlin