[fix] Use the byte length of the data (#2004)

Ensure that the correct length is used when framing the data.

Author: ronag

lib/sender.js

@@ -103,10 +103,10 @@ class Sender {
 
     let payloadLength = dataLength;
 
-    if (data.length >= 65536) {
+    if (dataLength >= 65536) {
       offset += 8;
       payloadLength = 127;
-    } else if (data.length > 125) {
+    } else if (dataLength > 125) {
       offset += 2;
       payloadLength = 126;
     }
@@ -136,11 +136,11 @@ class Sender {
     if (skipMasking) return [target, data];
 
     if (merge) {
-      applyMask(data, mask, target, offset, data.length);
+      applyMask(data, mask, target, offset, dataLength);
       return [target];
     }
 
-    applyMask(data, mask, data, 0, data.length);
+    applyMask(data, mask, data, 0, dataLength);
     return [target, data];
   }