Output class in exception when AutoRegister fails

When a public class that is wrongly configured or misplaced fails, it's
hard to debug. This is because it will fail because of a `getName()`
function call on a null object. To improve developer experience, output
the classname it fails on.

src/DependencyInjection/Compiler/AutoRegister.php

@@ -2,6 +2,7 @@
 
 namespace SimpleBus\SymfonyBridge\DependencyInjection\Compiler;
 
+use RuntimeException;
 use Symfony\Component\DependencyInjection\Compiler\CompilerPassInterface;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 
@@ -58,6 +59,11 @@ public function process(ContainerBuilder $container)
                         continue;
                     }
 
+                    if ($parameters[0]->getClass() === null) {
+                        throw new RuntimeException(sprintf('Could not get auto register class %s because the first parameter %s of public method %s should be have a class typehint. Either specify the typehint, make the function non-public, or disable auto registration.', $method->class,
+                            $parameters[0]->getName(), $method->getName()));
+                    }
+
                     // get the class name
                     $handles = $parameters[0]->getClass()->getName();