[boxes] do not write HTML markup for aside columns if no box content available (closes #3643330)

views/basetemplates.py

@@ -116,7 +116,5 @@
 @monkeypatch(basetemplates.TheMainTemplate)
 def nav_column(self, view, boxes, context):
     if boxes:
-        getlayout = self._cw.vreg['components'].select
-        self.w(u'<div id="aside-main-%s" class="col-md-3">\n' %
-               context)
+        html = []
         for box in boxes:
@@ -122,6 +120,11 @@
         for box in boxes:
-            box.render(w=self.w, view=view)
-        self.w(u'</div>\n')
+            box.render(w=html.append, view=view)
+        if html:
+            # only display aside columns if html availble
+            self.w(u'<div id="aside-main-%s" class="col-md-3">\n' %
+                   context)
+            self.w(u'\n'.join(html))
+            self.w(u'</div>\n')
     return len(boxes)
 
 @monkeypatch(basetemplates.TheMainTemplate)