Remove unnecessary null pointer checks

[elfring]

An extra null pointer check is not needed in functions like the following.

• USBD_AUDIO_DeInit
• USBD_HID_DeInit

[digitalentity]

Removing NULL pointer check there creates a potential NULL-pointer dereference bug. I strongly advise against removing there kinds of checks.

[digitalentity]

Moreover, those functions are not used by INAV and are optimized out by GCC

[elfring]

A POSIX compliant free() function will return immediately if a null pointer was passed. Thus I do not see a need to repeat such a sanity check.

[digitalentity]

If you would read the code you'll notice that a point is dereferenced first and then freed:

  /* DeInit  physical Interface components */
  if(pdev->pClassData != NULL)
  {
   ((USBD_AUDIO_ItfTypeDef *)pdev->pUserData)->DeInit(0);
    USBD_free(pdev->pClassData);
    pdev->pClassData = NULL;
  }

Regardless, we don't have dynamic memory allocation in INAV, these functions are not used and they are in a 3rd party library which may (and will) be updated eventually (discarding the fixes).