Merge pull request ClickHouse#167 from itrofimow/libcxx_string_view_fix

replace explicit string_view initialization from {nullptr, 0} with default ctor

Author: Enmk

clickhouse/columns/itemview.h

@@ -44,7 +44,7 @@ struct ItemView {
     }
 
     explicit ItemView()
-        : ItemView(Type::Void, {nullptr, 0})
+        : ItemView(Type::Void, {})
     {}
 
     template <typename T>