Merge pull request jdorn#698 from JElchison/dev-fix-bootstrap4-first-tab

Override getFirstTab() from themes.js to fix jdorn#681

Author: schmunk42

src/themes/bootstrap4.js

@@ -515,6 +515,10 @@ export class bootstrap4Theme extends AbstractTheme {
     return tabHolder.children[1].children[0]
   }
 
+  getFirstTab (holder) {
+    return holder.firstChild.firstChild.firstChild
+  }
+
   getProgressBar () {
     const min = 0
     const max = 100