Fix wrong condition

Author: Jérôme Poskin

Resources/views/Sitemap/sitemap.xml.twig

@@ -18,7 +18,7 @@
                         {% if image.path is defined %}
                             <image:loc>{{ image.path }}</image:loc>
                         {% endif %}
-                        {% if image.path is defined %}
+                        {% if image.caption is defined %}
                             <image:caption>{{ image.caption }}</image:caption>
                         {% endif %}
                         {% if image.geo_location is defined %}