Make workflows compatible with the dark theme

This CL also contains a minor fix for the workflows menu.

Fixed: twpowertools:146
Change-Id: I754e2695b3ee0f952b8f1c2f05af0533a715684c
diff --git a/src/contentScripts/communityConsole/workflows/components/index.js b/src/contentScripts/communityConsole/workflows/components/index.js
index 1822edc..05cf839 100644
--- a/src/contentScripts/communityConsole/workflows/components/index.js
+++ b/src/contentScripts/communityConsole/workflows/components/index.js
@@ -58,6 +58,8 @@
   }
 
   get _selectedWorkflow() {
+    if (!this._workflows) return null;
+
     for (const w of this._workflows) {
       if (w.uuid == this._selectedWorkflowUuid) return w.proto;
     }