Don't send empty messages

src/TextInputWidget.cc

@@ -133,6 +133,9 @@ FilteredTextEdit::minimumSizeHint() const
 void
 FilteredTextEdit::submit()
 {
+	if (toPlainText().trimmed().isEmpty())
+		return;
+
         if (true_history_.size() == INPUT_HISTORY_SIZE)
                 true_history_.pop_back();
         true_history_.push_front(toPlainText());