fix(router): disallow root segments with matrix params

modules/@angular/router/src/create_url_tree.ts

@@ -19,6 +19,8 @@ export function createUrlTree(
   }
 
   const normalizedCommands = normalizeCommands(commands);
+  validateCommands(normalizedCommands);
+
   if (navigateToRoot(normalizedCommands)) {
     return tree(urlTree.root, new UrlSegment([], {}), urlTree, queryParams, fragment);
   }
@@ -31,6 +33,12 @@ export function createUrlTree(
   return tree(startingPosition.segment, segment, urlTree, queryParams, fragment);
 }
 
+function validateCommands(n: NormalizedNavigationCommands): void {
+  if (n.isAbsolute && n.commands.length > 0 && (typeof n.commands[0] === 'object')) {
+    throw new Error('Root segment cannot have matrix parameters');
+  }
+}
+
 function tree(
     oldSegment: UrlSegment, newSegment: UrlSegment, urlTree: UrlTree, queryParams: Params,
     fragment: string): UrlTree {