patch 8.1.1878: negative float before method not parsed correctly

Problem:    Negative float before method not parsed correctly.
Solution:   Apply "!" and "-" in front of expression before using ->.
diff --git a/src/userfunc.c b/src/userfunc.c
index fd25090..bdd5c37 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -3165,8 +3165,9 @@
 	if (has_watchexpr())
 	    dbg_check_breakpoint(eap);
 
-	/* Handle a function returning a Funcref, Dictionary or List. */
-	if (handle_subscript(&arg, &rettv, !eap->skip, TRUE) == FAIL)
+	// Handle a function returning a Funcref, Dictionary or List.
+	if (handle_subscript(&arg, &rettv, !eap->skip, TRUE,
+							  name, &name) == FAIL)
 	{
 	    failed = TRUE;
 	    break;