patch 9.1.0590: Vim9: crash when accessing getregionpos() return value

Problem:  Vim9: crash when accessing getregionpos() return value.
Solution: Correct the return type (zeertzjq).

fixes: #15272
closes: #15273

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index 9adb7a5..c8baaf6 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -1969,6 +1969,17 @@
   getreginfo('').regcontents->assert_equal(['D1E2F3'])
 enddef
 
+def Test_getregionpos()
+  var lines =<< trim END
+    cursor(1, 1)
+    var pos = getregionpos(getpos('.'), getpos('$'))
+    for p in pos
+      assert_equal(bufnr('%'), p[0][0])
+    endfor
+  END
+  v9.CheckSourceDefSuccess(lines)
+enddef
+
 def Test_getregtype()
   var lines = ['aaa', 'bbb', 'ccc']
   setreg('a', lines)