Fixing a bug in index.js

Change-Id: I780911777af2ff3aada08f0abc12b0ff3c12c333

index.js

diff --git a/index.js b/index.js
index ae9515f..7c9fb6e 100644
--- a/index.js
+++ b/index.js
@@ -6,32 +6,34 @@
 var hasToStringTag = require('has-tostringtag/shams')();
 var getProto = Object.getPrototypeOf;
 
-class TrustedFunction {
-  static policy = self.trustedTypes.createPolicy('TrustedFunctionWorkaround', {
-    createScript: (_, ...args) => {
-       args.forEach( (arg) => {
-         if (!self.trustedTypes.isScript(arg)) {
-           throw new Error("TrustedScripts only, please");
-         }
-       });
+if (self.trustedTypes && self.trustedTypes.createPolicy) {
+	class TrustedFunction {
+  	static policy = self.trustedTypes.createPolicy('TrustedFunctionWorkaround', {
+    	createScript: (_, ...args) => {
+       	args.forEach( (arg) => {
+         	if (!self.trustedTypes.isScript(arg)) {
+           	throw new Error("TrustedScripts only, please");
+         	}
+       	});
        
-       // NOTE: This is insecure without parsing the arguments and body, 
-       // Malicious inputs  can escape the function body and execute immediately!
+       	// NOTE: This is insecure without parsing the arguments and body, 
+       	// Malicious inputs  can escape the function body and execute immediately!
        
-       const fnArgs = args.slice(0, -1).join(',');
-       const fnBody = args.pop().toString();
-       const body = `(function anonymous(
-       ${fnArgs}
-       ) {
-       ${fnBody}
-       })`;
-       return body;
-    }
-  });
+       	const fnArgs = args.slice(0, -1).join(',');
+       	const fnBody = args.pop().toString();
+       	const body = `(function anonymous(
+       	${fnArgs}
+       	) {
+       	${fnBody}
+       	})`;
+       	return body;
+    	}
+  	});
 
-  constructor(...args) {
-    return (window || self).eval(TrustedFunction.policy.createScript('', ...args));
-  } 
+  	constructor(...args) {
+    	return (window || self).eval(TrustedFunction.policy.createScript('', ...args));
+  	} 
+	}
 }
 
 var getGeneratorFunc = function () { // eslint-disable-line consistent-return