Better handle Request argument in no-fetch-if

As per internal feedback.

Related commit:
- gorhill/uBlock@ab06a01

Co-authored-by: Raymond Hill <rhill@raymondhill.net>

assets/resources/resources.txt

@@ -2129,16 +2129,21 @@ no-fetch-if.js application/javascript
 		apply: function(target, thisArg, args) {
 			let proceed = true;
 			try {
-				const url = args[0] instanceof self.Request
-					? args[0].url
-					: args[0];
-				const props = new Map([ [ 'url', url ] ]);
-				const init = args[1];
-				if ( init instanceof Object ) {
-					for ( let prop in init ) {
-						if ( init.hasOwnProperty(prop) === false ) { continue; }
-						props.set( prop, init[prop]);
+				let details;
+				if ( args[0] instanceof self.Request ) {
+					details = args[0];
+				} else {
+					details = Object.assign({ url: args[0] }, args[1]);
+				}
+				const props = new Map();
+				for ( let prop in details ) {
+					let v = details[prop];
+					if ( typeof v !== 'string' ) {
+						try { v = JSON.stringify(v); }
+						catch(ex) { }
 					}
+					if ( typeof v !== 'string' ) { continue; }
+					props.set(prop, v);
 				}
 				if ( log !== undefined ) {
 					const out = Array.from(props)