getVariableValues: unhandled errors

[Poweranimal]

Hi,

The possibly returned error from graphql.getVariableValues is unhandled.
See here: query-validation-visitor.js

This unhandled error causes serious side effects.

E.g.:
A query with variables has been submitted.
Getting the variables fails because of some reason (e.g. 'Cannot use GraphQLScalarType "Int" from another module or realm.\n\nEnsure that there is only one instance of "graphql" in the node_modules\ndirectory. If different versions of "graphql" are the dependencies of other\nrelied on modules, use "resolutions" to ensure only one version is installed.\n\nhttps://yarnpkg.com/en/docs/selective-version-resolutions\n\nDuplicate "graphql" modules cannot be used at the same time since different\nversions may have different capabilities and behavior. The data from one\nversion used in the function from another could produce confusing and\nspurious results.')
The returned result is undefined.
All passed variables of the query do not get validated.

Isues found because of: #225