Fix Errors in Breeding Cages

[davebridges]

There are two (probably javascript) errors in the breeding cage setup. For creating breeding cages, the mouse ID needs to be re-entered and then throws an error. For listing breeding cages nothing is shown. The traceback for the data entry error is:

File "/var/www/html/mousedb/mousedb/animal/models.py" in breeding_male_location_type
  246.             if int(self.breeding_males.all()[0].Cage) == int(self.Cage):

Exception Type: TypeError at /breeding_cage/985
Exception Value: int() argument must be a string or a number, not 'NoneType'