Fix Unreported: Run time error in UI code

Steps to reproduce:

1. Add clip to clip editor
2. Open the tracking settings & tracking settings extra panels

To fix this the sub panel is only drawn if a track is active.
The main panel will exit early and display a "No active track" message.
This is consistent with other panels in the clip editor.

Reviewed By: HooglyBoogly

Differential Revision: https://developer.blender.org/D9727

release/scripts/startup/bl_ui/space_clip.py

@@ -807,16 +807,19 @@ class CLIP_PT_track_settings(CLIP_PT_tracking_panel, Panel):
         layout.use_property_decorate = False
 
         clip = context.space_data.clip
+        active = clip.tracking.tracks.active
+
+        if not active:
+            layout.active = False
+            layout.label(text="No active track")
+            return
 
         col = layout.column()
+        col.prop(active, "motion_model")
+        col.prop(active, "pattern_match", text="Match")
 
-        active = clip.tracking.tracks.active
-        if active:
-            col.prop(active, "motion_model")
-            col.prop(active, "pattern_match", text="Match")
-
-            col.prop(active, "use_brute")
-            col.prop(active, "use_normalization")
+        col.prop(active, "use_brute")
+        col.prop(active, "use_normalization")
 
 
 class CLIP_PT_track_settings_extras(CLIP_PT_tracking_panel, Panel):
@@ -827,6 +830,12 @@ class CLIP_PT_track_settings_extras(CLIP_PT_tracking_panel, Panel):
     bl_parent_id = 'CLIP_PT_track_settings'
     bl_options = {'DEFAULT_CLOSED'}
 
+    @classmethod
+    def poll(cls, context):
+        clip = context.space_data.clip
+
+        return clip.tracking.tracks.active
+
     def draw(self, context):
         layout = self.layout
         layout.use_property_split = True