Fix T70965: Undo crash with specific file

Not sure how the WorkSpaceLayout.screen pointer could end up being NULL,
but apparently that happens, or at least happened with older files.

Rather than just adding NULL-checks, prefer not keeping around those
invalid layouts at all.

2 files changed, 11 insertions, 2 deletions

diff --git a/source/blender/blenkernel/intern/workspace.c b/source/blender/blenkernel/intern/workspace.c
index 3e449fa6b25..f58c20a7d72 100644
--- a/source/blender/blenkernel/intern/workspace.c
+++ b/source/blender/blenkernel/intern/workspace.c
@@ -247,8 +247,12 @@ WorkSpaceLayout *BKE_workspace_layout_add(Main *bmain,
 
 void BKE_workspace_layout_remove(Main *bmain, WorkSpace *workspace, WorkSpaceLayout *layout)
 {
-  id_us_min(&layout->screen->id);
-  BKE_id_free(bmain, layout->screen);
+  /* Screen should usually be set, but we call this from file reading to get rid of invalid
+   * layouts. */
+  if (layout->screen) {
+    id_us_min(&layout->screen->id);
+    BKE_id_free(bmain, layout->screen);
+  }
   BLI_freelinkN(&workspace->layouts, layout);
 }
 
diff --git a/source/blender/blenloader/intern/readfile.c b/source/blender/blenloader/intern/readfile.c
index 086f1db117d..fbe270dd060 100644
--- a/source/blender/blenloader/intern/readfile.c
+++ b/source/blender/blenloader/intern/readfile.c
@@ -3377,6 +3377,11 @@ static void lib_link_workspaces(FileData *fd, Main *bmain)
           }
         }
       }
+      else {
+        /* If we're reading a layout without screen stored, it's useless and we shouldn't keep it
+         * around. */
+        BKE_workspace_layout_remove(bmain, workspace, layout);
+      }
     }
 
     id->tag &= ~LIB_TAG_NEED_LINK;