Revert REST API init objects array (#231)

We didn't anticipated this was causing the REST API response to be changed for all consumers :
- before PR `"objects":null`
- after `"objects":[]`

We don't want that :/

We will instead fix collector-base (object of another PR, see #231)

This reverts commit 7243da3576.
This reverts commit 0940741568.

test/webservices/RestTest.php

@@ -180,7 +180,7 @@ JSON;
 		$this->assertContains($sExpectedJsonOuput, $this->DeleteTicketFromApi($iId));
 
 		$sExpectedJsonOuput=<<<JSON
-{"objects":[],"code":0,"message":"Found: 0"}
+{"objects":null,"code":0,"message":"Found: 0"}
 JSON;
 		$this->assertEquals($sExpectedJsonOuput, $this->GetTicketViaRest($iId));
 	}