Always cache values and add fid to feature hash

Author: m-kuhn

src/core/qgsexpression.cpp

@@ -697,8 +697,7 @@ static QVariant fcnAggregate( const QVariantList& values, const QgsExpressionCon
     subContext.appendScope( subScope );
     result = vl->aggregate( aggregate, subExpression, parameters, &subContext, &ok );
 
-    if ( ok )
-      context->setCachedValue( cacheKey, result );
+    context->setCachedValue( cacheKey, result );
   }
   else
   {

src/core/qgsfeature.cpp

@@ -323,6 +323,7 @@ uint qHash( const QgsFeature& key, uint seed )
   }
 
   hash ^= qHash( key.geometry().exportToWkt() );
+  hash ^= qHash( key.id() );
 
   return hash;
 }