added migration to fix emtpy units

set all units to none for all recipes containing empty named units and delete them

cookbook/migrations/0091_auto_20201226_1551.py

@@ -0,0 +1,27 @@
+# Generated by Django 3.1.4 on 2020-12-26 14:51
+
+from django.db import migrations
+
+
+def migrate_empty_units(apps, schema_editor):
+    Unit = apps.get_model('cookbook', 'Unit')
+    Step = apps.get_model('cookbook', 'Step')
+
+    empty_units = Unit.objects.filter(name='').all()
+    for x in empty_units:
+        for s in Step.objects.all():
+            for i in s.ingredients.all():
+                if i.unit == x:
+                    i.unit = None
+                    i.save()
+        x.delete()
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ('cookbook', '0090_auto_20201214_1359'),
+    ]
+
+    operations = [
+        migrations.RunPython(migrate_empty_units),
+    ]