Fix migrations

assets/migrations/0020_auto_20210302_1201.py

@@ -0,0 +1,23 @@
+# Generated by Django 3.1.7 on 2021-03-02 12:01
+
+from django.db import migrations
+
+
+def postgres_migration_prep(apps, schema_editor):
+    model = apps.get_model("assets", "Supplier")
+    fields = ["address", "email", "notes", "phone"]
+    for field in fields:
+        filter_param = {"{}__isnull".format(field): True}
+        update_param = {field: ""}
+        model.objects.filter(**filter_param).update(**update_param)
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('assets', '0019_fix_cabletype'),
+    ]
+
+    operations = [
+        migrations.RunPython(postgres_migration_prep, migrations.RunPython.noop)
+    ]