Simplify MetadataManager::getMaterializedView

Mixing handling of absence of object and catalog security in one 'if'
block was misleading. These two things are separate and unrelated so
the best if they handled in separately.

core/trino-main/src/main/java/io/trino/metadata/MetadataManager.java

@@ -1605,11 +1605,13 @@ public boolean isMaterializedView(Session session, QualifiedObjectName viewName)
     public Optional<MaterializedViewDefinition> getMaterializedView(Session session, QualifiedObjectName viewName)
     {
         Optional<ConnectorMaterializedViewDefinition> connectorView = getMaterializedViewInternal(session, viewName);
-        if (connectorView.isEmpty() || isCatalogManagedSecurity(session, viewName.getCatalogName())) {
-            return connectorView.map(view -> {
-                String runAsUser = view.getOwner().orElseThrow(() -> new TrinoException(INVALID_VIEW, "Owner not set for a run-as invoker view: " + viewName));
-                return createMaterializedViewDefinition(view, Identity.ofUser(runAsUser));
-            });
+        if (connectorView.isEmpty()) {
+            return Optional.empty();
+        }
+
+        if (isCatalogManagedSecurity(session, viewName.getCatalogName())) {
+            String runAsUser = connectorView.get().getOwner().orElseThrow(() -> new TrinoException(INVALID_VIEW, "Owner not set for a run-as invoker view: " + viewName));
+            return Optional.of(createMaterializedViewDefinition(connectorView.get(), Identity.ofUser(runAsUser)));
         }
 
         Identity runAsIdentity = systemSecurityMetadata.getViewRunAsIdentity(session, viewName.asCatalogSchemaTableName())