Showing a disabled menu items with a non-SVG icon generates Fyne error

[ErikKalkoken]

Checklist

• I have searched the issue tracker for open issues that relate to the same problem, before opening a new one.
• This issue only relates to a single bug. I will open new issues for any other problems.

Describe the bug

When trying to show a disabled menu items with a non-SVG icon we get the following error:

2025/02/26 11:53:13 Fyne error:  
2025/02/26 11:53:13   Cause: could not load SVG, falling back to static content: XML syntax error on line 5: invalid character entity &Ӎ� (no semicolon)
2025/02/26 11:53:13   At: /home/erik/go/fyne-dev/fyne/theme/icons.go:1408

The consequence of this bug is that non-SVG icons can currently not be used for menu items, if they might be disabled. They work fine though, for non-disabled menu items.

How to reproduce

1. Create a Fyne menu with at least one item
2. Add a non-SVG type resource as icon to the item (e.g. PNG or JPEG)
3. Disable the item
4. Show the menu

Screenshots

No response

Example code

package main

import (
	"fyne.io/fyne/v2"
	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/widget"
)

func main() {
	a := app.New()
	w := a.NewWindow("Menu icon demo")
	icon, err := fyne.LoadResourceFromURLString(
		"https://raw.githubusercontent.com/fyne-io/fyne/refs/heads/master/cmd/fyne_demo/data/assets/fyne.png")
	if err != nil {
		panic(err)
	}
	item := fyne.NewMenuItem("First", func() {})
	item.Icon = icon
	item.Disabled = true
	w.SetContent(container.NewCenter(widget.NewButton("Click me", func() {
		m := widget.NewPopUpMenu(fyne.NewMenu("", item), w.Canvas())
		m.Show()
	})))
	w.Resize(fyne.NewSize(600, 400))
	w.ShowAndRun()
}

Fyne version

2.5.4

Go compiler version

1.23.4

Operating system and version

Ubuntu 22.04

Additional Information

It looks like the bug is caused because Fyne always assuming the icon is a SVG image and tries to applies Disabled-theming to it:

menuItemRenderer.updateIcon()

This could be fixed by first checking if the icon really is a SVG image and leaving it alone if it is.

[ErikKalkoken]

Fix merged into develop: #5560