this fixes #456: another unrelated bug unveil from previous fix

platform/chromium/vapi-client.js

@@ -33,6 +33,13 @@
 
 self.vAPI = self.vAPI || {};
 
+// https://github.com/gorhill/uBlock/issues/456
+// Already injected?
+if ( vAPI.vapiClient ) {
+    return;
+}
+vAPI.vapiClient = true;
+
 var chrome = self.chrome;
 var vAPI = self.vAPI;