patch 8.2.3312: Vim9: after "if false" line breaks in expression not skipped

Problem:    Vim9: after "if false" line breaks in expression not skipped.
Solution:   Do parse the expression. (closes #8723)
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 2c5e3e7..059141a 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -2372,6 +2372,14 @@
   if false
     burp
   endif
+
+  # expression with line breaks skipped
+  if false
+      ('aaa'
+      .. 'bbb'
+      .. 'ccc'
+      )->setline(1)
+  endif
 enddef
 
 def Test_if_const_expr_fails()