allow empty amounts in constructor (null, empty string, 0.0) also they are not ints

src/Money/Money.php

@@ -38,6 +38,8 @@ class Money implements \JsonSerializable, Jsonable, Arrayable {
 	 * @throws MoneyException
 	 */
 	public function __construct($amount, $currency=null) {
+		if (empty($amount)) // FIX: if something empty is given (empty string, null, 0.0 etc) everything shoul work the same
+			$amount = 0;
 		if (!is_int($amount) && !ctype_digit($amount)) {
 			throw new MoneyException('Amount must be an integer');
 		}

tests/Money/MoneyTest.php

@@ -318,5 +318,12 @@ class MoneyTest extends \PHPUnit_Framework_TestCase {
 		$this->assertFalse($m5->isNegative());
 		$this->assertFalse($m6->isPositive());
 	}
-	 
+
+	public function testEmptyAmounts() {
+		$this->money(0);
+		$this->money('');
+		$this->money(null);
+		$this->money(0.00);
+		$this->isTrue();
+	}
 }