this fixes #464

src/js/contentscript-end.js

@@ -31,8 +31,17 @@
 
 /******************************************************************************/
 
+// https://github.com/gorhill/uBlock/issues/464
+if ( document instanceof HTMLDocument === false ) {
+    return false;
+}
+
+if ( !vAPI ) {
+    return;
+}
+
 if ( vAPI.canExecuteContentScript() !== true ) {
-    throw "uBlock> contentscript-end.js > Skipping " + location.protocol;
+    return;
 }
 
 // https://github.com/gorhill/uBlock/issues/456

src/js/contentscript-start.js

@@ -34,6 +34,11 @@
 
 /******************************************************************************/
 
+// https://github.com/gorhill/uBlock/issues/464
+if ( document instanceof HTMLDocument === false ) {
+    return false;
+}
+
 // Because in case
 if ( !vAPI ) {
     return;