vm_insnhelper.c: break in once

* vm_insnhelper.c (vm_throw_start): size of catch table has been
  included in iseq_catch_table struct, which could be NULL, since
  2.2.  e.g., proc-closure in `once'.
  [ruby-core:81775] [Bug #13680]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59181 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

test/ruby/test_exception.rb

@@ -1080,4 +1080,15 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
       }
     end;
   end
+
+  def test_break_in_once
+    assert_separately([], "#{<<-"begin;"}\n#{<<~'end;'}")
+    begin;
+      obj = Object.new
+      def obj.try
+        /#{break}/o
+      end
+      assert_raise(LocalJumpError, /proc-closure/) {obj.try}
+    end;
+  end
 end

vm_insnhelper.c

@@ -1083,13 +1083,13 @@ vm_throw_start(rb_thread_t *const th, rb_control_frame_t *const reg_cfp, enum ru
 
 	    while (escape_cfp < eocfp) {
 		if (escape_cfp->ep == ep) {
-		    const VALUE epc = escape_cfp->pc - escape_cfp->iseq->body->iseq_encoded;
-		    const rb_iseq_t * const iseq = escape_cfp->iseq;
-		    const struct iseq_catch_table * const ct = iseq->body->catch_table;
-		    const int ct_size = ct->size;
-		    int i;
+		    const rb_iseq_t *const iseq = escape_cfp->iseq;
+		    const VALUE epc = escape_cfp->pc - iseq->body->iseq_encoded;
+		    const struct iseq_catch_table *const ct = iseq->body->catch_table;
+		    unsigned int i;
 
-		    for (i=0; i<ct_size; i++) {
+		    if (!ct) break;
+		    for (i=0; i < ct->size; i++) {
 			const struct iseq_catch_table_entry * const entry = &ct->entries[i];
 
 			if (entry->type == CATCH_TYPE_BREAK &&