Do not cough on product with no variation types (onto 3.0.x)

Closes #3449825

modules/product/src/ContextProvider/ProductVariationContext.php

@@ -117,7 +117,7 @@ class ProductVariationContext implements ContextProviderInterface {
       $variation_types = array_keys($this->entityTypeBundleInfo->getBundleInfo('commerce_product_variation'));
     }
 
-    if (!($value instanceof ProductVariationInterface)) {
+    if (!($value instanceof ProductVariationInterface) && $variation_types) {
       if ($this->sampleEntityGenerator && !empty($layout_page)) {
         $value = $this->sampleEntityGenerator->get('commerce_product_variation', reset($variation_types));
       }