URL update on first load of themes page

## Description

Theme page is updating URL parameters with config upon first load of page. This should not happen, as there's nothing to print in the URL parameters.

## Steps to reproduce

1. Go to http://leonardocolor.io/
2. Click on "themes"
3. Observe the URL update to https://leonardocolor.io/theme.html?name=&config=%7B%22baseScale%22%3A%22%22%2C%22colorScales%22%3A%5B%5D%2C%22brightness%22%3A%2297%22%2C%22contrast%22%3A%221%22%7D

## Expected behavior

URL should remain clear of queries until something is entered into a field, or a color scale has been added

## Screenshots

## Environment
- **Browser(s) and OS(s):**
Version 80.0.3987.132 (Official Build) (64-bit) on macOS Catalina 10.15.3

## Additional context

Reproduce the issue by opening leonardocolor.io, selecting “themes,” and observing the initial URL. Trace the themes page initialization and URL parameter update, then verify that the URL stays query-free until a field is filled or a color scale is added.

Written by the indexing model from the issue text.