Fix T77541: Unregistering DATA_PT_modifiers doesn't remove modifier panels

This is a pretty quick fix; the solution is just removing all the
instanced panels whena panel is unregistered. This also necessitates
adding the option to call UI_panels_free_instanced with NULL context.

Differential Revision: https://developer.blender.org/D7977

1 files changed, 3 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_ui.c b/source/blender/makesrna/intern/rna_ui.c
index 9c9d10afa63..5228f00d0de 100644
--- a/source/blender/makesrna/intern/rna_ui.c
+++ b/source/blender/makesrna/intern/rna_ui.c
@@ -227,6 +227,9 @@ static void rna_Panel_unregister(Main *bmain, StructRNA *type)
                 }
               }
             }
+            /* The unregistered panel might have had a template that added instanced panels,
+             * so remove them just in case. They can be re-added on redraw anyway. */
+            UI_panels_free_instanced(NULL, region);
           }
         }
       }