fix improper variable initialisation

src/js/DefaultRules.tw

-//:: DefaultRules [script]
+:: DefaultRules [script]
 // jshint esversion: 6
 // jshint browser: true
 // this code applies RA rules onto slaves
 
 window.DefaultRules = (function() {
 	let V;
-	let r = "";
+	let r;
 
 	function DefaultRules(slave) {
 		console.log("default ruling for", slave);
 		V = State.variables;
+		r = "";
 		let rule = MergeRules(slave);
-		console.log("done merging", rule);
 
 		if (Object.keys(rule).length === 0) return r; // no rules apply