fix(custom): crash when clicking non-popup button

src/modules/custom/button.rs

@@ -43,7 +43,7 @@ impl CustomWidget for ButtonWidget {
                     ExecEvent {
                         cmd: exec.clone(),
                         args: None,
-                        id: button.popup_id(),
+                        id: button.try_popup_id().unwrap_or(usize::MAX), // may not be a popup button
                     }
                 );
             });

src/modules/mod.rs

@@ -115,17 +115,24 @@ impl ModulePopup for Option<gtk::Box> {
 }
 
 pub trait PopupButton {
+    fn try_popup_id(&self) -> Option<usize>;
     fn popup_id(&self) -> usize;
 }
 
 impl PopupButton for Button {
+    /// Gets the popup ID associated with this button, if there is one.
+    /// Will return `None` if this is not a popup button.
+    fn try_popup_id(&self) -> Option<usize> {
+        self.get_tag("popup-id").copied()
+    }
+
     /// Gets the popup ID associated with this button.
     /// This should only be called on buttons which are known to be associated with popups.
     ///
     /// # Panics
     /// Will panic if an ID has not been set.
     fn popup_id(&self) -> usize {
-        *self.get_tag("popup-id").expect("data to exist")
+        self.try_popup_id().expect("id to exist")
     }
 }