Connection line is not removed on undo

[Adeel Asghar]

• Load the attached package
• Open diagram of P.N
• Create a connection between m1 and m2
• Move m2 to a new position
• Undo the move operation by pressing ctrl+z. m2 moves back to the original position
• Undo again to delete the connection. The connection is deleted from the model but is still showing graphically.

[Adeel Asghar]

Fixed in b992a83/OpenModelica.