Fixes updates on distributions that are missing openjdk 8.

debian/control

 Package: jitsi-meet
 Architecture: all
 Depends: ${misc:Depends}, jitsi-videobridge, jitsi-meet-prosody, libjs-strophe (>= 1.1.3),
- libjs-jquery, libjs-jquery-ui, openjdk-8-jre-headless
+ libjs-jquery, libjs-jquery-ui, openjdk-8-jre-headless | nginx
 Description: WebRTC JavaScript video conferences
  Jitsi Meet is a WebRTC JavaScript application that uses Jitsi
  Videobridge to provide high quality, scalable video conferences.

debian/jitsi-meet.postinst

         # stores the hostname so we will reuse it later, like in purge
         db_set jitsi-meet/jvb-hostname $JVB_HOSTNAME
 
+        NGINX_INSTALL_CHECK="$(dpkg-query -W -f '${PackageSpec}:${Status}\n' nginx 2>&1 | grep -v "ok installed" || :)"
+        if [ -n "${NGINX_INSTALL_CHECK}" ]; then
+            FORCE_NGINX="false"
+        else
+            FORCE_NGINX="true"
+        fi
+
         # SSL for nginx
         db_get jitsi-meet/cert-choice
         CERT_CHOICE="$RET"