bbb-web: Added validation to freemarker template to verify image elements are...

bbb-web: Added validation to freemarker template to verify image elements are included when extension preview used

bigbluebutton-web/web-app/WEB-INF/freemarker/get-recordings.ftl

@@ -36,7 +36,7 @@
                   <#list properties?keys as property>
                   <#if property == "images">
                   <${property}>
-                    <#if properties[property]["image"]?is_hash>
+                    <#if properties[property]["image"]?? && properties[property]["image"]?is_hash>
                     <#assign image = properties[property]["image"]>
                     <image <#if image["attributes"]?? && image["attributes"]["width"]??>width="${image["attributes"]["width"]}"</#if> <#if image["attributes"]?? && image["attributes"]["height"]??>height="${image["attributes"]["height"]}"</#if> <#if image["attributes"]?? && image["attributes"]["alt"]??>alt="${image["attributes"]["alt"]}"</#if>>${image["text"]}</image>
                     <#elseif properties[property]["image"]?is_enumerable>