Filter unit only values when checking values defined

This prevents a false positive when the box control checks whether it has any unlinked values defined.

packages/components/src/box-control/utils.js

@@ -109,6 +109,13 @@ export function isValuesMixed( values = {} ) {
 export function isValuesDefined( values ) {
 	return (
 		values !== undefined &&
-		! isEmpty( Object.values( values ).filter( Boolean ) )
+		! isEmpty(
+			Object.values( values ).filter(
+				// Switching units when input is empty causes values only
+				// containing units. This gives false positive on mixed values
+				// unless filtered.
+				( value ) => !! value && /\d/.test( value )
+			)
+		)
 	);
 }