Relax validation for empty pages in PageValidations

Author: losipiuk

core/trino-main/src/main/java/io/trino/split/PageValidations.java

@@ -32,6 +32,11 @@ private PageValidations() {}
 
     public static void validateOutputPageTypes(SourcePage page, List<Type> expectedTypes, Supplier<String> debugContextSupplier)
     {
+        if (page.getPositionCount() == 0 && page.getChannelCount() == 0) {
+            // allow empty pages without blocks
+            return;
+        }
+
         if (page.getChannelCount() != expectedTypes.size()) {
             throw new TrinoException(
                     GENERIC_INTERNAL_ERROR,