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/stock/migrations/0100_auto_20230515_0004.py

@@ -0,0 +1,25 @@
+# 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'),
+        ('stock', '0099_alter_stockitem_status'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='stockitem',
+            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'),
+        ),
+        migrations.AlterField(
+            model_name='stocklocation',
+            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/stock/models.py

@@ -54,7 +54,7 @@ class StockLocation(InvenTreeBarcodeMixin, MetadataMixin, InvenTreeTree):
         verbose_name = _('Stock Location')
         verbose_name_plural = _('Stock Locations')
 
-    tags = TaggableManager()
+    tags = TaggableManager(blank=True)
 
     def delete_recursive(self, *args, **kwargs):
         """This function handles the recursive deletion of sub-locations depending on kwargs contents"""
@@ -324,7 +324,7 @@ class StockItem(InvenTreeBarcodeMixin, InvenTreeNotesMixin, MetadataMixin, commo
             }
         }
 
-    tags = TaggableManager()
+    tags = TaggableManager(blank=True)
 
     # A Query filter which will be re-used in multiple places to determine if a StockItem is actually "in stock"
     IN_STOCK_FILTER = Q(