Add unit test

CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 - modifier escape now triggers a E_USER_NOTICE when an unsupported escape type is used https://github.com/smarty-php/smarty/pull/649
 
+### Fixed
+- Fixed render crash when using inline include with a string template https://github.com/smarty-php/smarty/issues/639
+
 ## [3.1.39] - 2021-02-17
 
 ### Security

libs/sysplugins/smarty_internal_template.php

@@ -317,7 +317,7 @@ class Smarty_Internal_Template extends Smarty_Internal_TemplateBase
                 $tpl->template_resource = $template;
                 $tpl->cache_id = $cache_id;
                 $tpl->compile_id = $compile_id;
-                if (isset($uid)) {
+                if (isset($uid) && isset($tpl->compiled->file_dependency[ $uid ])) {
                     // for inline templates we can get all resource information from file dependency
                     list($filepath, $timestamp, $type) = $tpl->compiled->file_dependency[ $uid ];
                     $tpl->source = new Smarty_Template_Source($smarty, $filepath, $type, $filepath);

tests/UnitTests/TemplateSource/TagTests/Include/CompileIncludeTest.php

@@ -324,4 +324,12 @@ class CompileIncludeTest extends PHPUnit_Smarty
                      array("A{include file='include_spacing3.tpl'}B\nC", "AbarB\nC", '3_Newline3', $i++),
         );
     }
+
+	/**
+	 * Test Inline Include with string template
+	 */
+	public function testInlineStringInclude()
+	{
+		$this->assertEquals('include-inline', $this->smarty->fetch('inline_string_include.tpl'));
+	}
 }

tests/UnitTests/TemplateSource/TagTests/Include/templates/inline_string_include.tpl

@@ -0,0 +1 @@
+{include "string:include-inline" inline}