Fix ensure

Author: hasumikin

src/codegen_prism.inc

@@ -1091,6 +1091,7 @@ gen_ensure(mrc_codegen_scope *s, mrc_node *tree, uint32_t catch_entry, uint32_t
   CAST3(ensure, tree, ensure);
   int ensure_end, ensure_target;
   int idx;
+  push();
   ensure_end = ensure_target = s->pc;
   push();
   idx = cursp();

test/ensure_test.rb

@@ -0,0 +1,13 @@
+class EnsureTest < PicoRubyTest
+  desc "ensure arg"
+  assert_equal(<<~RUBY, "2\n1")
+    def m
+      begin
+        1
+      ensure
+        puts 2
+      end
+    end
+    puts m
+  RUBY
+end