Validate document nodes before use (#493)

* Validate document.body before use in loadScripts

This also fixes an issue where reject wasn't being passed to loadScriptSentinel.

* Validate document nodes before use in _getSiteColor

* Validate document.body before use in _getViewport

* Validate document.body before use in setContentScale

* Validate document.body before use in docImposterCreate

1 files changed, 8 insertions, 4 deletions

diff --git a/ext/mixed/js/dynamic-loader.js b/ext/mixed/js/dynamic-loader.js
index 29672d36..51b6821b 100644
--- a/ext/mixed/js/dynamic-loader.js
+++ b/ext/mixed/js/dynamic-loader.js
@@ -31,8 +31,13 @@ const dynamicLoader = (() => {
     }
 
     function loadScripts(urls) {
-        return new Promise((resolve) => {
+        return new Promise((resolve, reject) => {
             const parent = document.body;
+            if (parent === null) {
+                reject(new Error('Missing body'));
+                return;
+            }
+
             for (const url of urls) {
                 const node = parent.querySelector(`script[src='${escapeCSSAttribute(url)}']`);
                 if (node !== null) { continue; }
@@ -43,12 +48,11 @@ const dynamicLoader = (() => {
                 parent.appendChild(script);
             }
 
-            loadScriptSentinel(resolve);
+            loadScriptSentinel(parent, resolve, reject);
         });
     }
 
-    function loadScriptSentinel(resolve, reject) {
-        const parent = document.body;
+    function loadScriptSentinel(parent, resolve, reject) {
         const script = document.createElement('script');
 
         const sentinelEventName = 'dynamicLoaderSentinel';