Keep SyntaxData instead of Syntax alive in syntax node initializers

Author: ahoppen

Sources/SwiftSyntax/generated/syntaxNodes/SyntaxNodesTUVWXYZ.swift

@@ -279,11 +279,11 @@ public struct ThenStmtSyntax: StmtSyntaxProtocol, SyntaxHashable {
     // Extend the lifetime of all parameters so their arenas don't get destroyed
     // before they can be added as children of the new arena.
     let data: SyntaxData = withExtendedLifetime((SyntaxArena(), (
-            unexpectedBeforeThenKeyword, 
-            thenKeyword, 
-            unexpectedBetweenThenKeywordAndExpression, 
-            expression, 
-            unexpectedAfterExpression
+            unexpectedBeforeThenKeyword?.data, 
+            thenKeyword.data, 
+            unexpectedBetweenThenKeywordAndExpression?.data, 
+            expression.data, 
+            unexpectedAfterExpression?.data
           ))) { (arena, _) in
       let layout: [RawSyntax?] = [
           unexpectedBeforeThenKeyword?.raw,