Fix: Prevent using null as array offset in Package/PHP/Web (#228)

* Fix: Stop using null as array offset (Resolves #227)

* This also avoids accessing "path" on a null source when sourceInfo() returns null.

---------

Co-authored-by: lacatoire <louis-arnaud.catoire@external.drivalia.com>

phpdotnet/phd/Package/PHP/Web.php

@@ -204,7 +204,14 @@ $PARENTS = ' . var_export($parents, true) . ';';
             "alternatives" => $this->cchunk["alternatives"],
             "source" => $this->sourceInfo($id),
         );
-        $setup["history"] = $this->history[$setup["source"]["path"]] ?? [];
+        $history = $this->history ?? [];
+
+        $sourcePath = $setup["source"]["path"] ?? null;
+
+        $setup["history"] = $sourcePath !== null
+            ? ($history[$sourcePath] ?? [])
+            : [];
+
         if ($this->getChildren($id)) {
             $lang = $this->config->language;
             $setup["extra_header_links"] = array(