Input array with an empty string fails to be loaded

[matteo-cristino]

Detected a really strange behaviour when trying to load array with an mepty string in it.

To reproduce use the contract

Given I have a 'string array' named 'the_array'
Then print 'the array'

with data

{
    "the_array": [
        0,
        "a",
        "",
       "hello"
    ]
}

and you will get

[W]  JSON encoding error: table
[!]  Zencode runtime error
[!]  [source 'json']:88: invalid table: sparse array (n=3, #val=4)

This is returned only when the empty string is not the last element in the array, but in this case it is simply removed. For example using the above cotnract with data

{
    "the_array": [
        0,
        "a",
        ""
    ]
}

The result is

{
    "the_array": [
        0,
        "a"
    ]
}

Notice this behavior by updating zenroom in slangroom and tests start failing. Tests passed with zenroom 4.6.0 thus is something we have modified between it and latest commit.