It's not possible to exit the signature mode

Use case 1:

• Tools -> Digitally Sign -> select some area.
• Click Cancel in the certificate dialog.
• We are still in the signature mode.

Use case 2:

• Tools -> Digitally Sign -> select some area.
• Click OK in the certificate dialog.
• Click Cancel in the file dialog.
• We are still in the signature mode.

Use case 3:

• Tools -> Digitally Sign -> select some area.
• Click OK in the certificate dialog.
• Click Save in the file dialog.
• Close new Okular window and return to the previous one.
• We are still in the signature mode.