Fix wrong code in list/table model templates

rowCount should return 0 if the parent *is* valid, and return
the actual number of rows when queried with an invalid index.

Change-Id: I00e3d4ea79e1aaf0be1974da876c5a871d3924e6
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

share/qtcreator/templates/wizards/classes/itemmodel/listmodel.cpp

@@ -28,7 +28,7 @@ bool %{CN}::setHeaderData(int section, Qt::Orientation orientation, const QVaria
 
 int %{CN}::rowCount(const QModelIndex &parent) const
 {
-    if (!parent.isValid())
+    if (parent.isValid())
         return 0;
 
     // FIXME: Implement me!

share/qtcreator/templates/wizards/classes/itemmodel/tablemodel.cpp

@@ -29,7 +29,7 @@ bool %{CN}::setHeaderData(int section, Qt::Orientation orientation, const QVaria
 
 int %{CN}::rowCount(const QModelIndex &parent) const
 {
-    if (!parent.isValid())
+    if (parent.isValid())
         return 0;
 
     // FIXME: Implement me!
@@ -37,7 +37,7 @@ int %{CN}::rowCount(const QModelIndex &parent) const
 
 int %{CN}::columnCount(const QModelIndex &parent) const
 {
-    if (!parent.isValid())
+    if (parent.isValid())
         return 0;
 
     // FIXME: Implement me!