Allow deepAssign to delete props.

packages/gallery/src/utils/conversion.js

@@ -26,6 +26,8 @@ export function deepAssign(to, ...rest) {
 			const value = src[prop];
 			if (typeof value === 'object' && !Array.isArray(value)) {
 				to[prop] = deepAssign(to[prop] || {}, value);
+			} else if (value === undefined && to[prop] !== undefined) {
+				delete to[prop];
 			} else {
 				to[prop] = value;
 			}