Support template without parent

tests/samples/template_orphan.blp

@@ -0,0 +1,5 @@
+using Gtk 4.0;
+
+template $TestTemplate {
+  test-property: 'Hello, world';
+}

tests/samples/template_orphan.ui

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+DO NOT EDIT!
+This file was @generated by blueprint-compiler. Instead, edit the
+corresponding .blp file and regenerate this file with blueprint-compiler.
+-->
+<interface>
+  <requires lib="gtk" version="4.0"/>
+  <template class="TestTemplate">
+    <property name="test-property">Hello, world</property>
+  </template>
+</interface>

tests/test_samples.py

@@ -186,6 +186,7 @@ class TestSamples(unittest.TestCase):
                 "template_bind_property",
                 "template_id",
                 "template_no_parent",
+                "template_orphan",
                 "template_simple_binding",
                 "typeof",
                 "unchecked_class",
@@ -235,6 +236,7 @@ class TestSamples(unittest.TestCase):
         self.assert_decompile("strings_dec")
         self.assert_decompile("style_dec")
         self.assert_decompile("template")
+        self.assert_decompile("template_orphan")
         self.assert_decompile("translated")
         self.assert_decompile("using")
         self.assert_decompile("unchecked_class_dec")