don’t include region elements when empty (#4)

In small deployments, for instance when there is only one server for all
participants, the region doesn’t mean anything so we can remove the
elements instead of sending an empty value.

gst-meet/src/main.rs

@@ -36,8 +36,8 @@ struct Opt {
   video_codec: String,
   #[structopt(long, default_value = "gst-meet")]
   nick: String,
-  #[structopt(long, default_value)]
-  region: String,
+  #[structopt(long)]
+  region: Option<String>,
   #[structopt(long)]
   send_pipeline: Option<String>,
   #[structopt(long)]

lib-gst-meet-c/src/lib.rs

@@ -135,13 +135,18 @@ pub unsafe extern "C" fn gstmeet_connection_join_conference(
       return ptr::null_mut();
     },
   };
+  let region = if (*config).region.is_null() {
+    None
+  } else {
+    Some(CStr::from_ptr((*config).region)
+      .to_string_lossy()
+      .to_string())
+  };
   let config = JitsiConferenceConfig {
     muc,
     focus,
     nick: CStr::from_ptr((*config).nick).to_string_lossy().to_string(),
-    region: CStr::from_ptr((*config).region)
-      .to_string_lossy()
-      .to_string(),
+    region,
     video_codec: CStr::from_ptr((*config).video_codec)
       .to_string_lossy()
       .to_string(),

lib-gst-meet/src/conference.rs

@@ -76,7 +76,7 @@ pub struct JitsiConferenceConfig {
   pub muc: BareJid,
   pub focus: Jid,
   pub nick: String,
-  pub region: String,
+  pub region: Option<String>,
   pub video_codec: String,
   pub extra_muc_features: Vec<String>,
 }
@@ -453,18 +453,22 @@ impl StanzaFilter for JitsiConference {
           Element::builder("jitsi_participant_codecType", ns::DEFAULT_NS)
             .append(self.config.video_codec.as_str())
             .build(),
-          Element::builder("jitsi_participant_region", ns::DEFAULT_NS)
-            .append(self.config.region.as_str())
-            .build(),
           Element::builder("audiomuted", ns::DEFAULT_NS).append("false").build(),
           Element::builder("videomuted", ns::DEFAULT_NS).append("false").build(),
           Element::builder("nick", "http://jabber.org/protocol/nick")
             .append(self.config.nick.as_str())
             .build(),
-          Element::builder("region", "http://jitsi.org/jitsi-meet")
-            .attr("id", &self.config.region)
-            .build(),
         ];
+        if let Some(region) = &self.config.region {
+          presence.extend([
+            Element::builder("jitsi_participant_region", ns::DEFAULT_NS)
+              .append(region.as_str())
+              .build(),
+            Element::builder("region", "http://jitsi.org/jitsi-meet")
+              .attr("id", region)
+              .build(),
+          ]);
+        }
         presence.extend(
           self
             .config