Add fallback to percent_change_display (fixes #89)

shynet/dashboard/templatetags/helpers.py

@@ -61,6 +61,7 @@ def relative_stat_tone(
 
 @register.simple_tag
 def percent_change_display(start, end):
+    try:
         if start == None or end == None:
             return SafeString("Δ n/a")
         if start == end:
@@ -80,6 +81,8 @@ def percent_change_display(start, end):
                 pct_change = str(change) + "%"
 
         return SafeString(direction + pct_change)
+    except: # TODO: filter for specific issues
+        return SafeString("Δ ?")
 
 
 @register.inclusion_tag("dashboard/includes/sidebar_footer.html")