Self-reference to `$this` in `PelIfd::$maker_notes`

[saemy]

PelIfd::$maker_notes["parent"] is always $this (there is only one caller of PelIfd::setMakerNotes()). However, adding $this to the array leads to a reference of a PelIfd instance to itself. As a result that PelIfd instance can not be cleaned up right away after all references to it go away (as the ref_count remains at 1 - the one to itself). Only at garbage collection time the garbage cycle is detected and that instance is cleaned up.

This is an issue in case big images are processed one after another. In that scenario PelIfd::$maker_notes['data'] contains the full image data (i.e. multiple MB) and is only released upon garbage collection time - which is not right away. Garbage memory is piling up and running out of memory is easily possible and the program might crash with "Fatal error: Allowed memory size of xxx bytes exhausted".

[devbranch-vitaliy]

The same thing!
I tried to fix the issue with #7 but it didn't help me, the issue is still reproducible
In my case, more than 15 Jpeg images are processed one after another.
At the very least, we must provide protection against an infinite loop.

[saemy]

@devbranch-vitaliy Can you share one of those images s.t. I can try to reproduce? Thank you.