Fixed issue #719. Valentina crashes when unite pieces.

(grafted from ec7218525e9754a9237465d2c0a8656c5bccb387)

--HG--
branch : develop

ChangeLog.txt

@@ -32,6 +32,9 @@
 - [#706] Default unit in preferences not changing new file unit.
 - Fix bug. Valentina overrids exported file even if a user said no.
 - Fix bug. Date on label doesn't obey GUI language locale.
+- Tool Seam allowance's bounding box should not include passmarks.
+- Fix grainline position on layout.
+- [#719] Valentina crashes when unite pieces.
 
 # Version 0.5.0 May 9, 2017
 - [#581] User can now filter input lists by keyword in function wizard.

src/app/valentina/mainwindow.cpp

@@ -644,7 +644,7 @@ void MainWindow::ClosedDialog(int result)
         SCASSERT(scene != nullptr)
 
         QGraphicsItem *tool = dynamic_cast<QGraphicsItem *>(DrawTool::Create(dialogTool, scene, doc, pattern));
-        SCASSERT(tool != nullptr)
+        // Do not check for nullptr! See issue #719.
         ui->view->itemClicked(tool);
     }
     ArrowTool();