compile now does not crash when no tree is given (there are cases where we want to do a compile on just some nodes, without a CFunction object)
compile now does not crash when no tree is given (there are cases where we want to do a compile on just some nodes, without a CFunction object)

jonasfoe/COPASI,jonasfoe/COPASI,jonasfoe/COPASI,jonasfoe/COPASI,jonasfoe/COPASI,copasi/COPASI,copasi/COPASI,jonasfoe/COPASI,copasi/COPASI,copasi/COPASI,copasi/COPASI,jonasfoe/COPASI,copasi/COPASI,jonasfoe/COPASI,copasi/COPASI,copasi/COPASI,copasi/COPASI,jonasfoe/COPASI