Regression when invoking resolver methods that have arguments of primitive type

[lburja]

Description

Consider the following schema:

type Query {
    testOmittedBoolean(value: Boolean): Boolean
}

and the following resolver method:

boolean testOmittedBoolean(boolean value) {
    return value;
}

When executing the following query:

query {
    testOmittedBoolean
}

we get an exception:

[main] WARN notprivacysafe.graphql.execution.SimpleDataFetcherExceptionHandler - Exception while fetching data (/testOmittedBoolean) : null
java.lang.IllegalArgumentException: null
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at graphql.kickstart.tools.resolver.MethodFieldResolverDataFetcher.get(MethodFieldResolver.kt:261)
    at graphql.execution.ExecutionStrategy.fetchField(ExecutionStrategy.java:277)
    at graphql.execution.ExecutionStrategy.resolveFieldWithInfo(ExecutionStrategy.java:202)
    at graphql.execution.AsyncExecutionStrategy.execute(AsyncExecutionStrategy.java:74)
    at graphql.execution.Execution.executeOperation(Execution.java:167)
    at graphql.execution.Execution.execute(Execution.java:108)
    at graphql.GraphQL.execute(GraphQL.java:598)
    at graphql.GraphQL.parseValidateAndExecute(GraphQL.java:529)
    at graphql.GraphQL.executeAsync(GraphQL.java:493)
    at graphql.GraphQL.execute(GraphQL.java:426)
    at graphql.GraphQL.execute(GraphQL.java:398)
at graphql.kickstart.tools.ArgumentsTest.testOmittedBooleanArgument(ArgumentsTest.java:29)

Please note, that in the schema, the argument is optional, and in the resolver it is defined as a primitive ('boolean')

Expected behavior

In past releases, this used to work. If the argument was omitted, a default value of 'false' was passed in.
It broke recently due to the fixes related to #367
The expectation is that this query continues to work as before

Actual behavior

The query fails with an unexpected IllegalArgumentException

Steps to reproduce the bug

Run the following unit test:

public class ArgumentsTest {
    @Test
    public void testOmittedBooleanArgument() {
        GraphQLSchema schema = SchemaParser.newParser()
                .schemaString("" +
                        "type Query {" +
                        "   testOmittedBoolean(bool: Boolean): Boolean" +
                        "}")
                .resolvers(new Resolver())
                .build()
                .makeExecutableSchema();

        GraphQL gql = GraphQL.newGraphQL(schema).build();

        ExecutionResult result = gql
                .execute(ExecutionInput.newExecutionInput()
                        .query("" +
                                "query { " +
                                "  testOmittedBoolean" +
                                "}")
                        .context(new Object())
                        .root(new Object()));

        assertTrue(result.getErrors().isEmpty());
        assertEquals(false, ((Map<?, ?>) result.getData()).get("testOmittedBoolean"));
    }

    static class Resolver implements GraphQLQueryResolver {
        @SuppressWarnings("unused")
        public boolean testOmittedBoolean(boolean bool) {
            return bool;
        }
    }
}