Check for layer parent-child cycles.

[john-preston]

In case of bad input file there could be a cycle in parent-child relationship that leads to stack overflow crash. Simplest case is when the layer is made a parent to itself.

[smohantty]

@john-preston ,
I tried to reproduce your use case in After Effect. But After effect prevents assigning self assignment as well as cyclic parent . I understand maybe user can edit the json file and change the parent id. but then that is applicable to every property inside json file .

I think this fix should go inside the Model so that rendering code will be much simpler to maintain. as less unusual case to handle.

[john-preston]

Yes, the idea is to handle without crashing any json file the user offers.

I didn't understand where you think the checks for the cycles should go inside the Model and when should they be performed.

[smohantty]

What I meant is .. this checks should go inside lottieparser so that the renderer dosen't have to deal with all the checks to see if the layer is valid or not. If during resource parsing we find the layer data is corrupted then we can just remove that layer all together.
I have added a patch which checks for assigning parent to itself . you can add the patch to check for
cycle in layer parent tree after parsing the Layers.