Import fails with Cannot use "undefined" as a Firestore value if any field is NaN

[arthabus]

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Expected behavior

Import preserves NaN values and completes the import

Actual behavior

If a document contains NaN values, they are translated to "undefined" which makes firebase import fail

Steps to reproduce the behavior

   let profileData = {
        __collections__:{},
        nanField: parseFloat("sfg"),
    }

    const profileRef = firebase.firestore().doc(`users/${uid}`);
    await firestoreImport(profileData, profileRef)

[arthabus]

I guess adding (val !== val) to isScalar can fix that (this expression returns true in case of NaN)