Replace return; yield with yield from []

This has the same effect, but looks less hacky and makes PHPStan happy.
https://phpstan.org/r/df7fcc88-1df8-428e-b675-5dc6965c34d6

Previously this was needed to work properly with output capturing.

src/Node/BlockNode.php

@@ -42,7 +42,7 @@ class BlockNode extends Node
 
         $compiler
             ->subcompile($this->getNode('body'))
-            ->write("return; yield '';\n") // needed when body doesn't yield anything
+            ->write("yield from [];\n")
             ->outdent()
             ->write("}\n\n")
         ;