patch 8.2.4049: Vim9: reading before the start of the line with "$"

Problem:    Vim9: reading before the start of the line with "$" by itself.
Solution:   Do not subtract one when reporting the error.
diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index 01b4538..52237e3 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -2853,6 +2853,7 @@
   CheckDefAndScriptSuccess(lines)
 
   CheckDefAndScriptFailure(["var x = $$$"], ['E1002:', 'E15:'], 1)
+  CheckDefAndScriptFailure(["$"], ['E1002:', 'E15:'], 1)
 enddef
 
 def Test_expr7_register()