Have torrent.get_ratio return -1 when downloaded bytes is 0.

Have torrentview and statistics_tab display an infinity character when 
ratio is -1

deluge/core/torrent.py

@@ -410,19 +410,11 @@ class Torrent:
         else:
             status = self.status
 
-        up = status.all_time_upload
-        down = status.all_time_download
+        # Return -1.0 if the downloaded bytes is 0, this is to represent infinity
+        if status.all_time_download == 0:
+            return -1.0
 
-        # Convert 'up' and 'down' to floats for proper calculation
-        up = float(up)
-        down = float(down)
-
-        try:
-            ratio = up / down
-        except ZeroDivisionError:
-            return 0.0
-
-        return ratio
+        return float(status.all_time_upload) / float(status.all_time_download)
 
     def get_files(self):
         """Returns a list of files this torrent contains"""

deluge/ui/gtkui/listview.py

@@ -80,8 +80,8 @@ def cell_data_time(column, cell, model, row, data):
 def cell_data_ratio(column, cell, model, row, data):
     """Display value as a ratio with a precision of 3."""
     ratio = model.get_value(row, data)
-    if ratio == -1:
-        ratio_str = _("Unknown")
+    if ratio < 0:
+        ratio_str = "∞"
     else:
         ratio_str = "%.3f" % ratio
 

deluge/ui/gtkui/statistics_tab.py

@@ -46,6 +46,8 @@ def fpeer_size_second(first, second):
     return "%s (%s)" % (first, deluge.common.fsize(second))
 
 def fratio(value):
+    if value < 0:
+        return "∞"
     return "%.3f" % value
 
 def fpcnt(value):