fix messages with multiple empty frames (#61)

ws/session.nim

@@ -354,16 +354,15 @@ proc recv*(
         trace "Setting binary flag"
 
       let len = min(ws.frame.remainder.int, size - consumed)
-      if len <= 0:
-        trace "Nothing left to read, breaking!"
-        break
-
+      if len > 0:
         trace "Reading bytes from frame stream", len
         let read = await ws.stream.reader.readOnce(addr pbuffer[consumed], len)
         if read <= 0:
           trace "Didn't read any bytes, breaking"
           break
 
+        trace "Read data from frame", read
+
         if ws.frame.mask:
           trace "Unmasking frame"
           # unmask data using offset
@@ -375,7 +374,6 @@ proc recv*(
         consumed += read
         ws.frame.consumed += read.uint64
 
-      trace "Read data from frame", read
       # all has been consumed from the frame
       # read the next frame
       if ws.frame.remainder <= 0: