#1536 Crash when loading certain older files

[D. Michael McIntyre]

Reported on rosegarden-devel by Aere Greenway. Crash confirmed with test file. Looks like we try to access an invalid Instrument.

#0  0x00007fafc69f414a in Rosegarden::Instrument::getType (this=0x0) at /home/taco/SVN/rosegarden/src/base/Instrument.h:149
#1  0x00007fafc6a8748d in Rosegarden::RosegardenDocument::initialiseStudio (this=0x281d360)
    at /home/taco/SVN/rosegarden/src/document/RosegardenDocument.cpp:951
#2  0x00007fafc6a85bfa in Rosegarden::RosegardenDocument::openDocument (this=0x281d360, filename=..., permanent=true, squelchProgressDialog=false, 
    enableLock=true) at /home/taco/SVN/rosegarden/src/document/RosegardenDocument.cpp:655
#3  0x00007fafc6dbaccc in Rosegarden::RosegardenMainWindow::createDocumentFromRGFile (this=0x1f7d670, filePath=..., lock=true)
    at /home/taco/SVN/rosegarden/src/gui/application/RosegardenMainWindow.cpp:1686
#4  0x00007fafc6dba784 in Rosegarden::RosegardenMainWindow::createDocument (this=0x1f7d670, filePath=..., 
    importType=Rosegarden::RosegardenMainWindow::ImportRG4, lock=true) at /home/taco/SVN/rosegarden/src/gui/application/RosegardenMainWindow.cpp:1631
#5  0x00007fafc6db9a1f in Rosegarden::RosegardenMainWindow::openFile (this=0x1f7d670, filePath=..., type=Rosegarden::RosegardenMainWindow::ImportCheckType)
    at /home/taco/SVN/rosegarden/src/gui/application/RosegardenMainWindow.cpp:1500
#6  0x0000000000409497 in main (argc=2, argv=0x7ffc6b89bef8) at /home/taco/SVN/rosegarden/src/gui/application/main.cpp:710

[Ted Felix]

The file contains tracks which reference instruments that do not exist.

E.g. track 0 references instrument="3328". There is no instrument 3328 in any device.

This is an easy situation to end up in. Connect some tracks to a device, then delete that device. Now save and reload.

We used to handle this ok, but my new code to initialize the studio allows a NULL pointer to be dereferenced. This is easily fixed.

[Ted Felix]

Should be fixed in [r14776].

[Dave Plater]

Can confirm that this is fixed with patch to openSUSE's rosegarden-16.06