Fixed bug when not all hop times are filled

When hop times were left blank on boiling configuration, step timer didn't appear on GUI, neither the alert.

Alert time also fixed to be shown the entered amount of minutes before the end of boiling process. Not after the boiling start.

modules/base_plugins/brew_steps/__init__.py

@@ -201,9 +201,9 @@ class BoilStep(StepBase):
 
 
     def check_hop_timer(self, number, value):
-
-        if self.__getattribute__("hop_%s_added" % number) is not True and time.time() > (
-            self.timer_end - (int(self.timer) * 60 - int(value) * 60)):
+        if (value != ""
+            and self.__getattribute__("hop_%s_added" % number) is not True 
+            and (time.time() > (self.timer_end - int(value)*60))):
             self.__setattr__("hop_%s_added" % number, True)
             self.notify("Hop Alert", "Please add Hop %s" % number, timeout=None)