Add undefined check to gr-repo-access

This is to support Polymer 2 where you now have to handle undefined
values correctly in the observer or computing function.

Change-Id: Ia14f5ba0f02ab7cd170cf656ff5e2e9d58f24a67

polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.js

diff --git a/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.js b/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.js
index 7d2890a..7d47d08 100644
--- a/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.js
+++ b/polygerrit-ui/app/elements/admin/gr-repo-access/gr-repo-access.js
@@ -237,7 +237,7 @@
     },
 
     _computeWebLinkClass(weblinks) {
-      return weblinks.length ? 'show' : '';
+      return weblinks && weblinks.length ? 'show' : '';
     },
 
     _computeShowInherit(inheritsFrom) {
@@ -446,12 +446,12 @@
     },
 
     _computeSaveBtnClass(ownerOf) {
-      return ownerOf.length < 0 ? 'invisible' : '';
+      return ownerOf && ownerOf.length === 0 ? 'invisible' : '';
     },
 
     _computeMainClass(ownerOf, canUpload, editing) {
       const classList = [];
-      if (ownerOf.length > 0 || canUpload) {
+      if (ownerOf && ownerOf.length > 0 || canUpload) {
         classList.push('admin');
       }
       if (editing) {