patch 8.2.2771: Vim9: assignment not recognized if declaration was skipped

Problem:    Vim9: assignment not recognized if declaration was skipped.
Solution:   Also recognized an assignment if the variable does not exist.
            (closes #8108)
diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index 958b7b9..ad942a8 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -249,6 +249,18 @@
   END
 enddef
 
+def Test_skipped_assignment()
+  var lines =<< trim END
+      for x in []
+        var i: number = 1
+        while false
+          i += 1
+        endwhile
+      endfor
+  END
+  CheckDefAndScriptSuccess(lines)
+enddef
+
 def Test_assign_unpack()
   var lines =<< trim END
     var v1: number