gui: fix colorselect on unset

alacritty_config_gui.py

@@ -33,7 +33,8 @@ def delete_layout_items(layout):
 class ColorSelect(QtWidgets.QPushButton):
     def __init__(self, value):
         super().__init__()
-        self.set_value(value.replace('0x', '#'))
+        if value:
+            self.set_value(value.replace('0x', '#'))
         self.clicked.connect(self.handle_clicked)
 
     def handle_clicked(self):