Bugfix for subscriptions checksum calculation

[sergeuz]

handler.scope is an enum, and we want its address to be casted to uint8_t*, not its value

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Doneness:

• Contributor has signed CLA
• Problem and Solution clearly stated
• Code peer reviewed
• API tests compiled
• Run unit/integration/application tests on device
• Add documentation (N/A)
• Add to CHANGELOG.md after merging (add links to docs and issues)

BUGFIX

• Particle.subscribe() used with same events but changing scope between PUBLIC and PRIVATE or vice versa would potentially result in non-registered subscriptions. This was also crashing the GCC virtual device with a segfault when subscription checksums were calculated.

[technobly]

Looks easy enough but I want to understand what this impacts. What is the current issue, is it something that affects users and how will this alter it?

[technobly]

After adding a BUGFIX note, changes are approved :)

[monkbroc]

This also crashed the virtual device with a segfault

[technobly]

Thanks, I added that to the bugfix note.