array.c: Optimize rb_ary_and. Patch by Stefan Schüßler. [Fix GH-1938]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64755 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

array.c

@@ -4236,7 +4236,7 @@ rb_ary_and(VALUE ary1, VALUE ary2)
 
     ary2 = to_ary(ary2);
     ary3 = rb_ary_new();
-    if (RARRAY_LEN(ary2) == 0) return ary3;
+    if (RARRAY_LEN(ary1) == 0 || RARRAY_LEN(ary2) == 0) return ary3;
 
     if (RARRAY_LEN(ary1) <= SMALL_ARRAY_LEN && RARRAY_LEN(ary2) <= SMALL_ARRAY_LEN) {
 	for (i=0; i<RARRAY_LEN(ary1); i++) {