patch 9.0.0409: #{g:x} was seen as a curly-braces expression

Problem:    #{g:x} was seen as a curly-braces expression.
Solution:   Do never see #{} as a curly-braces expression. (closes #11075)
diff --git a/src/testdir/test_listdict.vim b/src/testdir/test_listdict.vim
index bf3117b..63ba47f 100644
--- a/src/testdir/test_listdict.vim
+++ b/src/testdir/test_listdict.vim
@@ -321,6 +321,10 @@
 
   " allow key starting with number at the start, not a curly expression
   call assert_equal({'1foo': 77}, #{1foo: 77})
+
+  " #{expr} is not a curly expression
+  let x = 'x'
+  call assert_equal(#{g: x}, #{g:x})
 endfunc
 
 " This was allowed in legacy Vim script