Allow 'notes' field in Part object to be blank

InvenTree/part/migrations/0029_auto_20200223_0901.py

@@ -0,0 +1,19 @@
+# Generated by Django 2.2.9 on 2020-02-23 09:01
+
+from django.db import migrations
+import markdownx.models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('part', '0028_auto_20200203_1007'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='part',
+            name='notes',
+            field=markdownx.models.MarkdownxField(blank=True, help_text='Part notes - supports Markdown formatting'),
+        ),
+    ]