Overlapping matches aren't handled correctly

## ISSUE
When running a rule that has overlapping matches as an FRule the frontend doesn't produce an error, making it look as if all is well. However, the transformation engine raises following exception:

```
Exception in thread Thread-18:
Traceback (most recent call last):
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\ptcal\pytcore\tcore\messages.py", line 241, in to_label_mapping
sourceNode = source_graph.get_node(self[label])
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\ptcal\pytcore\core\himesis.py", line 135, in get_node
raise KeyError('Node not found with specified id. Make sure to only create nodes via Himesis.add_node(): ' + str(guid))
KeyError: 'Node not found with specified id. Make sure to only create nodes via Himesis.add_node(): 1ce09e75-0052-4ece-89d0-acefa03f5ab0'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "C:\Users\Andrei\Downloads\atompm-portable\platform\WinPython\WPy32-3830\python-3.8.3\lib\threading.py", line 932, in _bootstrap_inner
self.run()
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\mtworker.py", line 26, in run
self._onmsg(self._msg)
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\mtworker.py", line 217, in _onmessage
getattr(self._ptcal,mode.lower())()
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\ptcal\ptcal.py", line 986, in step
self._doWhenLastStepFeedbackReceived(self._step)
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\ptcal\ptcal.py", line 169, in _doWhenLastStepFeedbackReceived
utils.doWhen(
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\ptcal\utils.py", line 20, in doWhen
callback()
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\ptcal\ptcal.py", line 1089, in _step
(res,ai) = runRule(nr)
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\ptcal\ptcal.py", line 1005, in runRule
self.packet = ar.packet_in(self.packet)
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\ptcal\pytcore\rules\frule.py", line 42, in packet_in
packet = self.W.packet_in(packet)
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\ptcal\pytcore\tcore\rewriter.py", line 46, in packet_in
mapping = match.to_label_mapping(packet.graph)
File "C:\Users\Andrei\Downloads\atompm-portable\AToMPM\mt\ptcal\pytcore\tcore\messages.py", line 243, in to_label_mapping
raise Exception('The matched node %s does not exist' % label)
Exception: The matched node 2 does not exist
```

I think this should be handled by the pytcore's resolver?

## HOW TO REPRODUCE?

Reproduce using following example:

Create a rule that looks as follows:


Schedule it as an FRule:


Apply the schedule to a model that has overlapping matches for aforementioned rule:


Observe as the rule is applied without producing an error in the frontend.

Reproduce the overlapping-match FRule scenario, then trace the failure through mt/ptcal/pytcore/tcore/messages.py, tcore/rewriter.py, rules/frule.py, and mt/ptcal/ptcal.py. Compare the transformation-engine exception with the frontend's current handling; done means the invalid overlapping-match result is surfaced as an error rather than appearing successful.

Written by the indexing model from the issue text.