avoid missing asset

operators/spreadsheet.py

@@ -571,6 +571,14 @@ class VSETB_OT_export_spreadsheet(Operator):
                     asset_castings = []
                     for asset_casting in strip.vsetb_strip_settings.casting:
                         asset = asset_casting.asset
+
+                        #print('------------------------')
+
+                        if not asset:
+                            self.report({"WARNING"}, f"The asset {asset_casting['_name']} is missing on strip {strip.name}")
+                            continue
+
+
                         if not asset.asset_type == cell.name:
                             continue