I'm assuming you have looked at the Document Checklist, the document that should guide your decisions about what is required to support your application.
One document that you will be required to submit is your last available NoA from CRA. That should show some income, I'm guessing.
If you are currently unemployed, which mat leave is not, technically, you can submit a letter from your employer, outlining your current situation, and also proof of your spouse's income along with the common-sense explanation that since you are spouses, your financial lives are entwined. You are on mat leave with his baby. And he will support you as any spouse would do under the circumstances.
Actual people will read your file. Appeal to the common sense of actual people.