Issue #519: Error: Crash with Union tool (dismine/valentina)

New issue 519: Error: Crash with Union tool https://bitbucket.org/valentinateam/valentina/issues/519/error-crash-with-union-tool

Susan Spencer:

Ubuntu 14.04, 64 bit Valentina v0.5.0.12719a build rev 62ae89e0dd7a

Tried to join two detail pieces.