[Bug]: Incorrect parsing of default values when GQL context variables are used

Consider the table definition for `type_table`:

The column `float_types` is a column which has a default value of `1.1`. Now, if we execute a GQL create mutation on this table and:

1. Provide input using GQL context variables
2. Omit value for the `float_types` column (since it has a default value so we don't need to specify it)

We get an error:

```json
{
"errors": [
{
"message": "Float cannot parse the given literal of type `StringValueNode`.",
"path": [
"item",
"float_types"
],
"extensions": {
"field": "CreateSupportedTypeInput.float_types",
"fieldType": "Float"
}
}
]
}
```

Similar behavior was observed when `int_types` was given a default value.