Incorrect use of || operator

[shicks]

zlib.js/src/zip.js

Line 82 in 24942f5

var filename = '' || opt_params['filename'];

I added a lint check for suspicious code and turned up this issue. Probably the operands wanted to be in the opposite direction so that a missing filename option would default to the empty string rather than undefined. But as it's written, the '' is always falsy so it just evaluates to undefined if no filename is given.