Only send message if its not null or not empty

This PR is raised to address the empty messages being sent in zipcall .

How to check the problem:-
1) Initiate a zipcall session
2) open chat 
3) continuously press enter,  you will be able to see multiple empty messages which is sent in the UI

public/js/chat.js

@@ -765,16 +765,24 @@ chatInput.addEventListener("keypress", function (event) {
     // Make links clickable
     msg = msg.autoLink();
     // Send message over data channel
+    if (isEmptyOrSpaces(msg) == false) {
     dataChanel.send("mes:" + msg);
-    // Add message to screen
     addMessageToScreen(msg, true);
+
+    }
+    // Add message to screen
     // Auto scroll chat down
     chatZone.scrollTop(chatZone[0].scrollHeight);
     // Clear chat input
     chatInput.value = "";
+    
   }
 });
 
+function isEmptyOrSpaces(str){
+    return str === null || str.match(/^ *$/) !== null;
+}
+
 // Called when a message is recieved over the dataChannel
 function handleRecieveMessage(msg) {
   // Add message to screen