Revert and fix send message session registry

Author: ackleymi

fix_string_test.go

@@ -44,6 +44,8 @@ func TestFIXStringRead(t *testing.T) {
 		expectError bool
 	}{
 		{[]byte("blah"), "blah", false},
+		{nil, "", false},
+		{[]byte(""), "", false},
 	}
 
 	for _, test := range tests {

registry.go

@@ -45,14 +45,10 @@ func Send(m Messagable) (err error) {
 
 	var senderCompID FIXString
 	if err := msg.Header.GetField(tagSenderCompID, &senderCompID); err != nil {
-
-		return nil
+		return err
 	}
 
-	var targetSubID FIXString
-	msg.Header.GetField(tagTargetSubID, &targetSubID)
-
-	sessionID := SessionID{BeginString: string(beginString), TargetCompID: string(targetCompID), SenderCompID: string(senderCompID), TargetSubID: string(targetSubID)}
+	sessionID := SessionID{BeginString: string(beginString), TargetCompID: string(targetCompID), SenderCompID: string(senderCompID)}
 
 	return SendToTarget(msg, sessionID)
 }