#3043779 "Source path has to start with a slash" exception when hitting path...

#3043779 "Source path has to start with a slash" exception when hitting path prefixed with index.php with RequestPath condition

Closes #3043779

core/modules/block/tests/src/Functional/BlockTest.php

@@ -80,6 +80,12 @@ public function testBlockVisibility(): void {
     // Confirm that an empty block is not displayed.
     $this->assertSession()->pageTextNotContains('Powered by Drupal');
     $this->assertSession()->responseNotContains('sidebar-first');
+
+    // Confirm that index.php followed by anything else does not cause an
+    // exception.
+    $this->drupalGet('/index.php' . $this->randomMachineName());
+    $this->assertSession()->statusCodeEquals(200);
+    $this->assertSession()->pageTextNotContains($title);
   }
 
   /**