patch 8.1.0740: Tcl test fails

Problem:    Tcl test fails.
Solution:   When the argument is empty don't give an error, instead rely on
            the error reporting higher up.

src/eval.c

@@ -6462,7 +6462,9 @@ get_name_len(
     }
 
     len += get_id_len(arg);
-    if (len == 0 && verbose)
+    // Only give an error when there is something, otherwise it will be
+    // reported at a higher level.
+    if (len == 0 && verbose && **arg != NUL)
 	EMSG2(_(e_invexpr2), *arg);
 
     return len;