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()
diff --git a/src/version.c b/src/version.c
index be49f09..cf0665c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4049,
+/**/
     4048,
 /**/
     4047,
diff --git a/src/vim9expr.c b/src/vim9expr.c
index 83c68a9..edaee50 100644
--- a/src/vim9expr.c
+++ b/src/vim9expr.c
@@ -1233,7 +1233,7 @@
     len = get_env_len(arg);
     if (len == 0)
     {
-	semsg(_(e_syntax_error_at_str), start - 1);
+	semsg(_(e_syntax_error_at_str), start);
 	return FAIL;
     }