Fix  'getChecks' is undefined

This only happens when removing _legacyUndefinedCheck

Change-Id: Icd7e47e640338e1f77692ab9b8d479c9556d1d78
diff --git a/gr-checks/gr-checks-chip-view.js b/gr-checks/gr-checks-chip-view.js
index a2933ef..ce7d6d5 100644
--- a/gr-checks/gr-checks-chip-view.js
+++ b/gr-checks/gr-checks-chip-view.js
@@ -128,6 +128,8 @@
      * @param {function(number, number): !Promise<!Object>} getChecks
      */
     _fetchChecks(change, revision, getChecks) {
+      if (!getChecks || !change || !revision) return;
+
       getChecks(change._number, revision._number).then(checks => {
         this.set('_hasChecks', checks.length > 0);
         if (checks.length > 0) {
diff --git a/gr-checks/gr-checks-view.js b/gr-checks/gr-checks-view.js
index 81c851d..c0d32a1 100644
--- a/gr-checks/gr-checks-view.js
+++ b/gr-checks/gr-checks-view.js
@@ -140,6 +140,8 @@
      * @param {function(number, number): !Promise<!Object>} getChecks
      */
     _fetchChecks(change, revision, getChecks) {
+      if (!getChecks || !change || !revision) return;
+
       getChecks(change._number, revision._number).then(checks => {
         if (checks && checks.length) {
           checks.sort(this._orderChecks);