create object even if it can't be signed

Signed-off-by: Maxence Lange <maxence@artificial-owl.com>

lib/Service/SignatureService.php

@@ -259,7 +259,7 @@ class SignatureService {
 		try {
 			$signature->sign();
 			$object->setSignature($signature);
-		} catch (LinkedDataSignatureMissingException $e) {
+		} catch (Exception $e) {
 		}
 	}