Fix errors with empty database

CHANGELOG.md

@@ -1,4 +1,5 @@
 ## Unreleased
+* Fix errors with empty database
 * Fix negative playtimes being considered positive
 * Add %d for days to common.util.time.format_duration
 * Set up tests, add tests for common.util.time

src/web/tracker/views.py

@@ -104,12 +104,12 @@ def add_platform(request):
 def index(request):
     context = {}
     if Session.objects.count() == 0:
-        duration_value = 0
+        duration: str = ""
     else:
         result = Session.objects.all().aggregate(Sum("duration_calculated"))
-        context["total_duration"] = format_duration(
+        duration = format_duration(
             result["duration_calculated__sum"], "%H hours %m minutes"
         )
-    context["total_duration"] = duration_value
+    context["total_duration"] = duration
     context["title"] = "Index"
     return render(request, "index.html", context)