backups panels show only when the asset has data

plugins/backups/plugin.py

@@ -91,7 +91,7 @@ class BackupsPlugin(BasePlugin):
         panels = [kind.infopanel() for kind in REGISTRY.values()
                   if kind.infopanel()]
         for position, kind in enumerate(REGISTRY.values()):
-            panels.append({
+            panel = {
                 'id': 'backups-{}'.format(kind.key),
                 'title': kind.displayname,
                 'assettypes': list(kind.assettypes),
@@ -105,7 +105,6 @@ class BackupsPlugin(BasePlugin):
                         {'key': 'shorthash', 'label': 'Hash', 'mono': True},
                     ],
                 },
-                'empty': kind.emptytext,
                 # The generic renderer has no per-item actions, and downloading
                 # a .reg needs a per-revision control plus a dialect choice, so
                 # the panel links to the plugin's own history view instead.
@@ -115,7 +114,16 @@ class BackupsPlugin(BasePlugin):
                     'emptylabel': 'View history',
                 },
                 'position': 40 + position,
-            })
+            }
+            # OMIT 'empty' entirely unless the kind sets it. The list renderer
+            # shows a panel when it has rows OR declares empty text, so a
+            # present-but-null 'empty' would still render the panel on every
+            # asset of the type. Most machines are not part markers and never
+            # will be, so that panel must disappear rather than announce it has
+            # nothing.
+            if kind.emptytext:
+                panel['empty'] = kind.emptytext
+            panels.append(panel)
         return panels
 
     def get_settings_defaults(self) -> List[Dict]: