Fix build.

src/Columns/IColumn.h

@@ -308,7 +308,7 @@ public:
     {
         MutablePtr res = ptr->shallowMutate(); /// Now use_count is 2.
         ptr.reset(); /// Reset use_count to 1.
-        res->forEachSubcolumn([](WrappedPtr & subcolumn) { subcolumn = IColumn::mutate(std::move(subcolumn)); });
+        res->forEachSubcolumn([](WrappedPtr & subcolumn) { subcolumn = IColumn::mutate(std::move(subcolumn).detach()); });
         return res;
     }
 

src/Common/COW.h

@@ -216,7 +216,8 @@ protected:
 
         operator const immutable_ptr<T> & () const { return value; }
         operator immutable_ptr<T> & () { return value; }
-        operator immutable_ptr<T> () && { return std::move(value); }
+
+        immutable_ptr<T> detach() && { return std::move(value); }
 
         operator bool() const { return value != nullptr; }
         bool operator! () const { return value == nullptr; }