sqlitetablemodel: Don't insert new rows when there is no new data

When not getting any data from query we'd tell Qt that we're about to
insert data anyway and cause confusion this way. At least this might
cause some trouble on some systems.

This issue tries to deal with issue #565.

src/sqlitetablemodel.cpp

@@ -478,8 +478,12 @@ void SqliteTableModel::fetchData(unsigned int from, unsigned to)
     }
     sqlite3_finalize(stmt);
 
-    beginInsertRows(QModelIndex(), currentsize, m_data.size()-1);
-    endInsertRows();
+    // Check if there was any new data
+    if(m_data.size() > currentsize)
+    {
+        beginInsertRows(QModelIndex(), currentsize, m_data.size()-1);
+        endInsertRows();
+    }
 }
 
 void SqliteTableModel::buildQuery()