patch 8.2.2503: Vim9: a caught error may leave something on the stack

Problem:    Vim9: a caught error may leave something on the stack.
Solution:   Drop items from the stack if needed. (closes #7826)
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index 42a0d61..17b996f 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -556,6 +556,16 @@
     n = 411
   endtry
   assert_equal(411, n)
+
+  var counter = 0
+  for i in range(4)
+    try
+      eval [][0]
+    catch
+    endtry
+    counter += 1
+  endfor
+  assert_equal(4, counter)
 enddef
 
 def Test_cnext_works_in_catch()