Clean up admin class extension

Co-authored-by: Aiky30 <Aiky30@users.noreply.github.com>

Author: adam-murray

djangocms_snippet/admin.py

@@ -9,9 +9,20 @@
 from .views import SnippetPreviewView
 
 
+
+# Use the version mixin if djangocms-versioning is installed and enabled
+snippet_admin_classes = [admin.ModelAdmin]
+
 try:
     from djangocms_versioning.admin import ExtendedVersionAdminMixin
 
+    if  SnippetCMSAppConfig.djangocms_versioning_enabled:
+        snippet_admin_classes += [ExtendedVersionAdminMixin]
+except ImportError:
+    pass
+    
+    from djangocms_versioning.admin import ExtendedVersionAdminMixin
+
     djangocms_versioning_installed = True
 except ImportError:
     djangocms_versioning_installed = False