patch 9.0.0218: reading before the start of the line

Problem:    Reading before the start of the line.
Solution:   When displaying "$" check the column is not negative.
diff --git a/src/edit.c b/src/edit.c
index 0b0d174..0b78964 100644
--- a/src/edit.c
+++ b/src/edit.c
@@ -1746,8 +1746,9 @@
  * Only works when cursor is in the line that changes.
  */
     void
-display_dollar(colnr_T col)
+display_dollar(colnr_T col_arg)
 {
+    colnr_T col = col_arg < 0 ? 0 : col_arg;
     colnr_T save_col;
 
     if (!redrawing())