Enable rule `array-callback-return`

We had two cases that we forgot the return for a `map`
when we should have one.

Enabling the eslintrule can help us prevent from that.

Change-Id: I20d7ccbf32cfe6e43bbeb6f6c87211f429b5c588
diff --git a/polygerrit-ui/app/.eslintrc.js b/polygerrit-ui/app/.eslintrc.js
index 6acf222..c402297 100644
--- a/polygerrit-ui/app/.eslintrc.js
+++ b/polygerrit-ui/app/.eslintrc.js
@@ -74,6 +74,7 @@
     "no-multiple-empty-lines": ["error", {"max": 1}],
     "no-prototype-builtins": "off",
     "no-redeclare": "off",
+    'array-callback-return': ['error', { allowImplicit: true }],
     "no-restricted-syntax": [
       "error",
       {
diff --git a/polygerrit-ui/app/elements/settings/gr-gpg-editor/gr-gpg-editor.js b/polygerrit-ui/app/elements/settings/gr-gpg-editor/gr-gpg-editor.js
index 6c6ad01..d1bc7eb 100644
--- a/polygerrit-ui/app/elements/settings/gr-gpg-editor/gr-gpg-editor.js
+++ b/polygerrit-ui/app/elements/settings/gr-gpg-editor/gr-gpg-editor.js
@@ -72,9 +72,8 @@
   }
 
   save() {
-    const promises = this._keysToRemove.map(key => {
-      this.$.restAPI.deleteAccountGPGKey(key.id);
-    });
+    const promises = this._keysToRemove
+        .map(key => this.$.restAPI.deleteAccountGPGKey(key.id));
 
     return Promise.all(promises).then(() => {
       this._keysToRemove = [];
diff --git a/polygerrit-ui/app/elements/settings/gr-ssh-editor/gr-ssh-editor.js b/polygerrit-ui/app/elements/settings/gr-ssh-editor/gr-ssh-editor.js
index d869128..9c819e9 100644
--- a/polygerrit-ui/app/elements/settings/gr-ssh-editor/gr-ssh-editor.js
+++ b/polygerrit-ui/app/elements/settings/gr-ssh-editor/gr-ssh-editor.js
@@ -63,9 +63,8 @@
   }
 
   save() {
-    const promises = this._keysToRemove.map(key => {
-      this.$.restAPI.deleteAccountSSHKey(key.seq);
-    });
+    const promises = this._keysToRemove
+        .map(key => this.$.restAPI.deleteAccountSSHKey(key.seq));
 
     return Promise.all(promises).then(() => {
       this._keysToRemove = [];
diff --git a/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text.js b/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text.js
index 039b95d..862c48c 100644
--- a/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text.js
+++ b/polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text.js
@@ -83,7 +83,7 @@
 
     // Add new content.
     for (const node of this._computeNodes(this._computeBlocks(content))) {
-      container.appendChild(node);
+      if (node) container.appendChild(node);
     }
   }
 
@@ -276,7 +276,7 @@
       if (block.type === 'quote') {
         const bq = document.createElement('blockquote');
         for (const node of this._computeNodes(block.blocks)) {
-          bq.appendChild(node);
+          if (node) bq.appendChild(node);
         }
         return bq;
       }
@@ -300,6 +300,9 @@
         }
         return ul;
       }
+
+      console.warn('Unrecognized type.');
+      return;
     });
   }
 }
diff --git a/polygerrit-ui/app/services/gr-auth.js b/polygerrit-ui/app/services/gr-auth.js
index 555cb23..21081cc 100644
--- a/polygerrit-ui/app/services/gr-auth.js
+++ b/polygerrit-ui/app/services/gr-auth.js
@@ -158,6 +158,7 @@
         result = c.substring(key.length);
         return true;
       }
+      return false;
     });
     return result;
   }