Fix Merged::generateLinesReplace()

- Mess Detector reported unused variable. Although always created and
  used, it's nicer to declare it on beforehand.

Author: DigiLive

lib/jblond/Diff/Renderer/Html/Merged.php

@@ -199,6 +199,7 @@ public function generateLinesReplace(array $changes): string
             }
 
             // Capture added parts.
+            $addedParts = [];
             preg_match_all('/\x0.*?\x1/', $changes['changed']['lines'][$lineNo], $addedParts, PREG_PATTERN_ORDER);
             array_unshift($addedParts[0], '');