thread.c: check type of coverage

* thread.c (update_coverage): check type of coverage array not
  only if non-zero.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@54075 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

thread.c

@@ -4774,7 +4774,7 @@ static void
 update_coverage(rb_event_flag_t event, VALUE proc, VALUE self, ID id, VALUE klass)
 {
     VALUE coverage = rb_iseq_coverage(GET_THREAD()->cfp->iseq);
-    if (coverage && RBASIC(coverage)->klass == 0) {
+    if (RB_TYPE_P(coverage, T_ARRAY) && !RBASIC_CLASS(coverage)) {
 	long line = rb_sourceline() - 1;
 	long count;
 	if (RARRAY_AREF(coverage, line) == Qnil) {