Fix automatic identification of module name in AbstractBlock when module namespace is not explicit in template file location

This issue affects all modules starting with word Block

Exception #0 (Magento\Framework\Exception\ValidatorException): Invalid template file: 'template.phtml' in module: 'Vendor' block's name: 'my-block'

Author: rodrigowebjump

lib/internal/Magento/Framework/View/Element/AbstractBlock.php

@@ -874,7 +874,7 @@ public static function extractModuleName($className)
         $namespace = substr(
             $className,
             0,
-            strpos($className, '\\' . 'Block')
+            strpos($className, '\\' . 'Block' . '\\')
         );
         return str_replace('\\', '_', $namespace);
     }