Allow tag fields to be empty (#4816)

Without this change, editing items (e.g. via the admin interface) fails if the tag field is not empty

InvenTree/part/migrations/0107_alter_part_tags.py

@@ -0,0 +1,20 @@
+# Generated by Django 3.2.19 on 2023-05-15 00:04
+
+from django.db import migrations
+import taggit.managers
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('taggit', '0005_auto_20220424_2025'),
+        ('part', '0106_part_tags'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='part',
+            name='tags',
+            field=taggit.managers.TaggableManager(blank=True, help_text='A comma-separated list of tags.', through='taggit.TaggedItem', to='taggit.Tag', verbose_name='Tags'),
+        ),
+    ]

InvenTree/part/models.py

@@ -380,7 +380,8 @@ class Part(InvenTreeBarcodeMixin, InvenTreeNotesMixin, MetadataMixin, MPTTModel)
     """
 
     objects = PartManager()
-    tags = TaggableManager()
+
+    tags = TaggableManager(blank=True)
 
     class Meta:
         """Metaclass defines extra model properties"""