Use more correct ?? operator instead of ?: where possible

The only reason this code uses ?: is that it was available much
earlier, since PHP 5.3, while ?? was only available since PHP 7.0.

?? is more specific and gets only activated on null, while ?: is
more relaxed and gets activated on any "falsy" value. While that
can be useful it's unspecific and fragile and just not needed in
these places.

Change-Id: Ibe24e9c67faab1fdea4feb0f09b8d62c973b23af

Author: thiemowmde

src/Entity/Item.php

@@ -68,9 +68,9 @@ public function __construct(
 		?StatementList $statements = null
 	) {
 		$this->id = $id;
-		$this->fingerprint = $fingerprint ?: new Fingerprint();
-		$this->siteLinks = $siteLinks ?: new SiteLinkList();
-		$this->statements = $statements ?: new StatementList();
+		$this->fingerprint = $fingerprint ?? new Fingerprint();
+		$this->siteLinks = $siteLinks ?? new SiteLinkList();
+		$this->statements = $statements ?? new StatementList();
 	}
 
 	/**

src/Entity/Property.php

@@ -71,9 +71,9 @@ public function __construct(
 		?StatementList $statements = null
 	) {
 		$this->id = $id;
-		$this->fingerprint = $fingerprint ?: new Fingerprint();
+		$this->fingerprint = $fingerprint ?? new Fingerprint();
 		$this->setDataTypeId( $dataTypeId );
-		$this->statements = $statements ?: new StatementList();
+		$this->statements = $statements ?? new StatementList();
 	}
 
 	/**

src/Statement/Statement.php

@@ -67,8 +67,8 @@ public function __construct(
 		?string $guid = null
 	) {
 		$this->mainSnak = $mainSnak;
-		$this->qualifiers = $qualifiers ?: new SnakList();
-		$this->references = $references ?: new ReferenceList();
+		$this->qualifiers = $qualifiers ?? new SnakList();
+		$this->references = $references ?? new ReferenceList();
 		$this->setGuid( $guid );
 	}
 

src/Term/Fingerprint.php

@@ -47,9 +47,9 @@ public function __construct(
 		?TermList $descriptions = null,
 		?AliasGroupList $aliasGroups = null
 	) {
-		$this->labels = $labels ?: new TermList();
-		$this->descriptions = $descriptions ?: new TermList();
-		$this->aliasGroups = $aliasGroups ?: new AliasGroupList();
+		$this->labels = $labels ?? new TermList();
+		$this->descriptions = $descriptions ?? new TermList();
+		$this->aliasGroups = $aliasGroups ?? new AliasGroupList();
 	}
 
 	/**