Fix psalm errors

Author: rawilk

psalm.xml.dist

@@ -1,6 +1,6 @@
 <?xml version="1.0"?>
 <psalm
-    errorLevel="4"
+    errorLevel="5"
     findUnusedVariablesAndParams="true"
     resolveFromConfigFile="true"
     useDocblockPropertyTypes="true"

src/Support/Name.php

@@ -113,7 +113,7 @@ protected function wantsPossessive(string $key): bool
     public function __get(string $key): ?string
     {
         if ($this->wantsPossessive($key)) {
-            $key = Str::replaceLast('possessive', null, $key);
+            $key = Str::replaceLast('possessive', '', $key);
 
             return $this->possessive($this->{$key});
         }