parser/pageparser: Fix Org Mode summary delimiter assignment

Closes #13152

parser/pageparser/pagelexer_intro.go

@@ -91,14 +91,14 @@ func lexFrontMatterOrgMode(l *pageLexer) stateFunc {
 		#+DESCRIPTION: Just another golang parser for org content!
 	*/
 
-	l.summaryDivider = summaryDividerOrg
-
 	l.backup()
 
 	if !l.hasPrefix(delimOrg) {
 		return lexMainSection
 	}
 
+	l.summaryDivider = summaryDividerOrg
+
 	// Read lines until we no longer see a #+ prefix
 LOOP:
 	for {