fix useragent issue on ios chrome (#28712)

examples/jsm/loaders/GLTFLoader.js

@@ -2586,10 +2586,14 @@ class GLTFParser {
 
 		if ( typeof navigator !== 'undefined' ) {
 
-			isSafari = /^((?!chrome|android).)*safari/i.test( navigator.userAgent ) === true;
-			safariVersion = isSafari ? navigator.userAgent.match( /Version\/(\d+)/ )[ 1 ] : - 1;
-			isFirefox = navigator.userAgent.indexOf( 'Firefox' ) > - 1;
-			firefoxVersion = isFirefox ? navigator.userAgent.match( /Firefox\/([0-9]+)\./ )[ 1 ] : - 1;
+			const userAgent = navigator.userAgent;
+
+			isSafari = /^((?!chrome|android).)*safari/i.test( userAgent ) === true;
+			const safariMatch = userAgent.match( /Version\/(\d+)/ );
+			safariVersion = isSafari && safariMatch ? parseInt( safariMatch[ 1 ], 10 ) : - 1;
+
+			isFirefox = userAgent.indexOf( 'Firefox' ) > - 1;
+			firefoxVersion = isFirefox ? userAgent.match( /Firefox\/([0-9]+)\./ )[ 1 ] : - 1;
 
 		}