Public date and copyright year missing for CVE-2020-1945 in OVAL

I have previously filed a similar bug:
https://bugs.launchpad.net/ubuntu-cve-tracker/+bug/1856009

When reading the OVAL file, the public_date tag contains "unknown", and the rights tag says "Copyright (C) unknown Canonical Ltd.". Maybe another test for you to add :)

Here's the definition from the OVAL file.

```
<definition class="vulnerability" id="oval:com.ubuntu.bionic:def:202019450000000" version="1">
    <metadata>
        <title>CVE-2020-1945 on Ubuntu 18.04 LTS (bionic) - medium.</title>
        <description>It was discovered that Apache Ant created temporary files with insecure permissions. An attacker could use this vulnerability to
read sensitive information leaked into /tmp, or potentially inject malicious code into a project that is built with Apache Ant.</description>
        <affected family="unix">
            <platform>Ubuntu 18.04 LTS</platform>
        </affected>
        <reference source="CVE" ref_id="CVE-2020-1945" ref_url="https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-1945" />
        <advisory>
            <severity>Medium</severity>
            <rights>Copyright (C) unknown Canonical Ltd.</rights>
            <public_date>unknown</public_date>
            <assigned_to>msalvatore</assigned_to>
            <discovered_by>Mike Salvatore</discovered_by>
            <crd>unknown</crd>
            <ref>http://people.canonical.com/~ubuntu-security/cve/2020/CVE-2020-1945.html</ref>
        </advisory>
    </metadata>
    <criteria>
        <extend_definition definition_ref="oval:com.ubuntu.bionic:def:100" comment="Ubuntu 18.04 LTS (bionic) is installed." applicability_check="true" />
        <criterion test_ref="oval:com.ubuntu.bionic:tst:202019450000000" comment="ant package in bionic is affected and needs fixing." />
    </criteria>
</definition>
```

From https://people.canonical.com/~ubuntu-security/oval/com.ubuntu.bionic.cve.oval.xml.bz2. Present as of May 15 2020 13:23:00 UTC, first seen May 15 2020 05:00:58 UTC.

Kind regards.