check an existence of block.

* gc.c (rb_raw_obj_info): check block before using it.

* vm_core.h (vm_block_iseq): r61565 introduced NULL check but this
  check is only needed by `rb_raw_obj_info()` and it is called at GC
  debug mode. Above fix for `rb_raw_obj_info()` solves this problem and
  NULL check should not be needed any more.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61571 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

gc.c

@@ -9346,8 +9346,12 @@ rb_raw_obj_info(char *buff, const int buff_size, VALUE obj)
 	    break;
 	  }
 	  case T_DATA: {
+	    const struct rb_block *block;
 	    const rb_iseq_t *iseq;
-	    if (rb_obj_is_proc(obj) && (iseq = vm_proc_iseq(obj)) != NULL) {
+	    if (rb_obj_is_proc(obj) &&
+		(block = vm_proc_block(obj)) != NULL &&
+		(vm_block_type(block) == block_type_iseq) &&
+		(iseq = vm_block_iseq(block)) != NULL) {
 		rb_raw_iseq_info(buff, buff_size, iseq);
 	    }
 	    else {

vm_core.h

@@ -1406,7 +1406,6 @@ vm_proc_ep(VALUE procval)
 static inline const rb_iseq_t *
 vm_block_iseq(const struct rb_block *block)
 {
-    if (!block) return NULL;
     switch (vm_block_type(block)) {
       case block_type_iseq: return rb_iseq_check(block->as.captured.code.iseq);
       case block_type_proc: return vm_proc_iseq(block->as.proc);