[widevine] Fix bad data pointer on clrb_out variable

[CastagnaIT]

Description

Premise, i havent understood the data target format of dataOut
this prevents me from understanding how the data should be composed/constructed in to dataOut

from my investigations i found that:
dataOut.UseData() was used to get and store current data pointer but after that, many times is used "AppendData",
this method before append data check if the internal buffer of AP4_DataBuffer is enough to store data if not re-create the internal buffer, and so the data pointer before stored (to clrb_out) will point to a bad memory address causing the segmentation fault crash

NOTE: the crash affect most of times aarch64/ARM64 cpu's, other systems looks like problem remains hidden maybe due to system optimization the "old" memory address still working

Motivation and context

fix #1394
fix #1452

How has this been tested?

Tested am@zon VOD videos episodes on:
CoreElec with aarch64 cpu
Android nvidia shield pro
Windows

Screenshots (if appropriate):

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

Checklist:

• I have read the Contributing document
• My code follows the Code Guidelines of this project
• My change requires a change to the Wiki documentation
• I have updated the documentation accordingly

[glennguy]

Thanks! Looks like this would have been a PITA to chase down, great work

[CastagnaIT]

quite... in the future more likely would better add code comments to explain data construction that at least for me is not so immediately clear