Fix #856

[lukatolo]

Also fix the color of donut during targeting and fix Navigation() references

[rmatsuda]

Hi Luka! Thanks for the PR. Its returning the following error when navigation starts:

File "C:\repository\main-invesalius\invesalius3\invesalius\gui\task_navigator.py", line 1622, in OnStartNavigationButton
Publisher.sendMessage("Start navigation")
File "C:\repository\main-invesalius\invesalius3\invesalius\pubsub\pub.py", line 74, in sendMessage
Publisher.sendMessage(topicName, **msgdata)
File "C:\Users\renan\anaconda3\envs\invesalius-cp311\Lib\site-packages\pubsub\core\publisher.py", line 216, in sendMessage
topicObj.publish(**msgData)
File "C:\Users\renan\anaconda3\envs\invesalius-cp311\Lib\site-packages\pubsub\core\topicobj.py", line 452, in publish
self.__sendMessage(msgData, topicObj, msgDataSubset)
File "C:\Users\renan\anaconda3\envs\invesalius-cp311\Lib\site-packages\pubsub\core\topicobj.py", line 482, in __sendMessage
listener(data, self, allData)
File "C:\Users\renan\anaconda3\envs\invesalius-cp311\Lib\site-packages\pubsub\core\listener.py", line 237, in call
cb(**kwargs)
File "C:\repository\main-invesalius\invesalius3\invesalius\gui\task_navigator.py", line 1609, in OnStartNavigation
self.navigation.StartNavigation(self.tracker, self.icp)
File "C:\repository\main-invesalius\invesalius3\invesalius\navigation\navigation.py", line 685, in StartNavigation
self.pedal_connector.add_callback("navigation", self.PedalStateChanged)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'add_callback'

[lukatolo]

Fixed the careless mistake. It works in single coil mode now.

For targeting with multiple coils, it should work correctly, but the the color of the donut MAY not change correctly to green. This is irrelevant though, since the next PR will change the multicoil target GUI

[rmatsuda]

Thanks! It's working now. Another thing, the Hide Coil button should also hide the fixed target coil, when target mode is on. So we can see the brain structures behind the target.