Fixing warning fields.W340

ippisite/ippidb/models.py

@@ -373,7 +373,7 @@ class Ppi(AutoFillableModel):
     symmetry = models.ForeignKey(Symmetry, models.CASCADE)
     diseases = models.ManyToManyField(Disease, null=True, blank=True)
     family = models.ForeignKey(PpiFamily, models.CASCADE, null=True, blank=True)
-    name = models.TextField('PPI name', null=True, blank=True)
+    name = models.TextField('PPI name', blank=True)
 
     def __str__(self):
         return 'PPI #{} on {}'.format(self.id, self.name)