ScriptFu: fix #11954 err call PDB file-export-foo type GimpExportOption

GimpExportOptions is incomplete.
It exists so the API is stable.
For now, ScriptFu eat and ignore actual args,
binding to NULL, in calls to PDB procedures
file-export-foo having formal args of this type.

Unlikely that in the future ScriptFu will do anything else:
if a plugin needs export options, use another language.
The few file exporters used by existing ScriptFu scripts
(file-gbr-export and file-pat-export)
don't honor export options.

plug-ins/script-fu/scripts/paste-as-pattern.scm

@@ -33,6 +33,7 @@
         (file-pat-export RUN-NONINTERACTIVE
                        pattern-image
                        path
+                       -1  ; NULL ExportOptions
                        name)
 
         (gimp-image-delete pattern-image)