Detect sends on closed websocket explicitly.

It turns out that send on a closed websocket doesn't throw, so handle
this case explicitly.  Thanks to Giuseppe Castagna for noticing.

static/sfu.js

@@ -67,10 +67,13 @@ Connection.prototype.close = function(sendit) {
     this.pc.close();
 
     if(sendit) {
+        try {
             send({
                 type: 'close',
                 id: this.id,
             });
+        } catch(e) {
+        }
     }
 };
 
@@ -526,7 +529,6 @@ function serverConnect() {
 
     return new Promise((resolve, reject) => {
         socket.onerror = function(e) {
-            console.error(e);
             reject(e.error ? e.error : e);
         };
         socket.onopen = function(e) {
@@ -534,14 +536,21 @@ function serverConnect() {
             resetChat();
             setConnected(true);
             let up = getUserPass();
+            try {
                 send({
                     type: 'handshake',
                     id: myid,
                     group: group,
                     username: up.username,
                     password: up.password,
-            });
+                })
                 sendRequest(document.getElementById('requestselect').value);
+                } catch(e) {
+                    console.error(e);
+                    displayError(e);
+                    reject(e);
+                    return;
+                }
             resolve();
         };
         socket.onclose = function(e) {
@@ -730,6 +739,10 @@ async function addIceCandidates(conn) {
 function send(m) {
     if(!m)
         throw(new Error('Sending null message'));
+    if(socket.readyState !== socket.OPEN) {
+        // send on a closed connection doesn't throw
+        throw(new Error('Connection is not open'));
+    }
     return socket.send(JSON.stringify(m));
 }
 
@@ -993,14 +1006,19 @@ function handleInput() {
         return;
     }
 
-    addToChatbox(myid, username, message, me);
-    send({
+    try {
+        let a = send({
             type: 'chat',
             id: myid,
             username: username,
             value: message,
             me: me,
         });
+        addToChatbox(myid, username, message, me);
+    } catch(e) {
+        console.error(e);
+        displayError(e);
+    }
 }
 
 document.getElementById('inputform').onsubmit = function(e) {