Description:
------------
If a prepared statement is executed while the bound variable doesn't 
exist, or is NULL, PHP freeze and wait. 

I tweaked the test also to use SQLITE3_NULL instead of SQLITE3_TEXT, and 
NULL or !isset($foo) also froze PHP. 

Reproduce code:
---------------
<?php
$db = new SQLite3(':memory:');

// cr?ation d'une table
$db->exec('CREATE TABLE test (time INTEGER, id STRING)');

$db->exec("INSERT INTO test (time, id) VALUES (" . time() . ", 'a')");
$db->exec("INSERT INTO test (time, id) VALUES (" . time() . ", 'b')");

$stmt = $db->prepare("SELECT * FROM test WHERE id = ? ORDER BY id ASC");

//$foo = 'a'; works OK 
//$foo = NULL; also freeze
$stmt->bindParam(1, $foo, SQLITE3_TEXT);
$results = $stmt->execute();
while ($result = $results->fetchArray(SQLITE3_NUM))
{
	var_dump($result);
}
$results->finalize();

$db->close();
?>



Expected result:
----------------
I would expect PHP to return from execute with an error. 

Actual result:
--------------
PHP freeze, doing nothing.