Remedy CVE-2018-12913

[iibclothier]

This was originally reported in #90 which was closed without any remediation.

This can be reproduced by downloading the POC from here:
https://github.com/Edward-L/my-cve-list/blob/master/miniz/dos-an-infinite-loop-miniz_tinfl-c-398.poc

Uncomment the assert in the miniz_tinfl.c line 494, build the project.

And then run the example3.exe as shown with debugger:

example3.exe d, "C:\Temp\dos-an-infinite-loop-miniz_tinfl-c-398.poc" "C:\Temp\Bad.txt"

Because the POC file used as the input is not a valid zip file, we should not be attempting to extract it. However, as a guard against other zip files that may be maliciously crafted, we've added the condition and throw an error if both sym2 and counter are zero.