Fix undefined and unused variables

1. +++ b/src/Tests/WebformRenderingTest.php
   @@ -99,11 +99,9 @@ class WebformRenderingTest extends WebformTestBase {
   +    //
   

   We don't need to add this space.

2. +++ b/src/Tests/WebformRenderingTest.php
   @@ -88,7 +88,7 @@ class WebformRenderingTest extends WebformTestBase {
   -    
   +    //
        // Check plain text email.
        $this->assertEqual($text_email['subject'], 'submission label (&>');
        $this->assertEqual($text_email['params']['subject'], 'submission <em>label</em> (&><#)');
   @@ -99,11 +99,9 @@ class WebformRenderingTest extends WebformTestBase {
   
   @@ -99,11 +99,9 @@ class WebformRenderingTest extends WebformTestBase {
        // $this->assertContains($text_email['params']['body'], 'textfield_special_characters (&amp;&gt;: (&amp;&gt;&lt;#){default_value}(&amp;&gt;&lt;#)');
        // $this->assertContains($text_email['params']['body'], 'text_format_basic_html:');
        // $this->assertContains($text_email['params']['body'], '/{default_value}/');
   -
   -    /**************************************************************************/
   +    //
        // Submission.
   -    /**************************************************************************/
   ...
   +    //
   

   I don't think we need to restructure these comments.

+++ b/src/WebformEntityStorage.php
@@ -226,7 +226,7 @@ class WebformEntityStorage extends ConfigEntityStorage implements WebformEntityS
-    $transaction = $this->database->startTransaction();

We can't remove this variable, please see the comment. The $txn in the comment should be changed to $transctions.

The $webform variable in webform.api.php file in line 66 provides an example of how to get the current webform. It should not be changed or removed.