patch 8.2.1533: Vim9: error when passing getreginfo() result to setreg()

Problem:    Vim9: error when passing getreginfo() result to setreg().
Solution:   Use dict_get_bool() for "isunnamed". (closes #6784)
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 412e4a6..2c23a0e 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -1419,6 +1419,13 @@
    setlocal ts=8
 enddef
 
+def Test_setreg()
+  setreg('a', ['aaa', 'bbb', 'ccc'])
+  let reginfo = getreginfo('a')
+  setreg('a', reginfo)
+  assert_equal(reginfo, getreginfo('a'))
+enddef 
+
 def Fibonacci(n: number): number
   if n < 2
     return n