Fix potential divide by zero.

If there are no bytes attributable to APP, then you get a divide
by zero. Modify the code to avoid doing a divide by zero.

This can happen when using logwrapper to enable malloc debug.

Test: Ran on a heap that had no APP bytest.
Change-Id: I48f0666a92b591e4537c493c56b136e517a36c25
1 file changed