patch 9.0.0373: Coverity warns for NULL check and unused return value

Problem:    Coverity warns for NULL check and unused return value.
Solution:   Remove the NULL check, it was already checked earlier.  Add (void)
            to ignore the return value.
diff --git a/src/ex_eval.c b/src/ex_eval.c
index 61d2881..2f31b3e 100644
--- a/src/ex_eval.c
+++ b/src/ex_eval.c
@@ -925,7 +925,7 @@
 	}
 	else if (*p == '$')
 	    ++p;
-	get_name_len(&p, &alias, FALSE, FALSE);
+	(void)get_name_len(&p, &alias, FALSE, FALSE);
     }
     name_only = ends_excmd2(arg, skipwhite(p));
     vim_free(alias);