Description:
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For every bloomfilter i create with this extensions, the method has() always returns true when passed an empty string. btw, thanks for your time doing it, it's really useful.

Reproduce code:
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$bf = new BloomFilter(3, 0.0001);
$bf->add("foo");
$bf->add("bar");
$bf->add("xyz");

var_dump($bf->has("foo"));
var_dump($bf->has("blabla"));
var_dump($bf->has(""));

Expected result:
----------------
true
false
false

Actual result:
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true
false
true