Fixed problem which prevented constant expressions to be calculated.
Fixed problem which prevented constant expressions to be calculated.

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