Getting string index out of range error when invoking copybook:toJson API

[MohamedSabthar]

Description:
Conducer the following code

Steps to reproduce:

import ballerinax/copybook;
import ballerina/io;

public function main() returns error? {
    copybook:Convertor converter = check new ("copybook.cpy");
    map<json> jsonInput = {"Decimal": 10};
    string copybook = check converter.toCopybook(jsonInput);
    io:println(copybook);
}

Following is the copybook definition

01 Decimal    PIC 9(2).99.

expected:
10.00

getting:

error: {ballerina/lang.string}StringOperationError {"message":"string index out of range. Length:'1' requested: '0' to '2'"}

Affected Versions:

OS, DB, other environment details and versions:

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