Return some zero's when recipe is empty.

Get rid of errors.
closes #12

beer/models.py

@@ -173,6 +173,9 @@ class BatchRecipe(CustomModel):
 
     @property
     def net_kettle_deadspace(self):
+        if self.equipment is None:
+            return 0
+
         # If hops in kettle deadspace
         # No deadspace if its all filled with hop trub
         if self.equipment.hops_remain_kettle:
@@ -183,14 +186,20 @@ class BatchRecipe(CustomModel):
 
     @property
     def kettle_hose_loss(self):
+        if self.equipment is None:
+            return 0
         return float(self.equipment.kettle_plumbing_loss)
 
     @property
     def kettle_dead_space(self):
+        if self.equipment is None:
+            return 0
         return float(self.equipment.kettle_deadspace)
 
     @property
     def boil_off_gph(self):
+        if self.equipment is None:
+            return 0
         return float(self.equipment.kettle_boil_rate)
 
     @property
@@ -212,7 +221,7 @@ class BatchRecipe(CustomModel):
             17: '8D4C32', 18: '7C452D', 19: '6B3A1E', 20: '5D341A',
             21: '4E2A0C', 22: '4A2727', 23: '361F1B', 24: '261716',
             25: '231716', 26: '19100F', 27: '16100F', 28: '120D0C',
-            29: '100B0A', 30: '050B0A'
+            29: '100B0A', 30: '050B0A', 0: 'C1963C'
         }
 
         return '#{}'.format(srm_hex_lookup[int(self.srm)])
@@ -220,7 +229,10 @@ class BatchRecipe(CustomModel):
     @property
     def bu_gu(self):
         gu = (self.original_sg - 1) * 1000
+        try:
             return self.ibu_tinseth / gu
+        except ZeroDivisionError:
+            return 0
 
     @property
     def rbr(self):  # .75 needs to be calculated number...