Fix falsy string and int query values

[ant-roli]

#133 and #177 fixed this for input objects, but not query values.

Sending a 0 value on an int with min constraint or an empty string on a string with minLength constraint would skip validation previously.

Making the values non-nullable doesn't help, and using defaults (in a resolver) can help, but not for all cases. For instance for an auth query you don't want to give a username a default and cause db queries for something that should be failing validation.

See #187 for an example of the problem.

[coveralls]

Pull Request Test Coverage Report for Build 5778877049

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.03%) to 94.855%

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Totals
Change from base Build 5619996352:	0.03%
Covered Lines:	357
Relevant Lines:	366

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💛 - Coveralls