Merge #3956

3956: Fix out of bounds in editor render image r=heinrich5991 a=Jupeyy

## Checklist

- [x] Tested the change ingame
- [ ] Provided screenshots if it is a visual change
- [ ] Tested in combination with possibly related configuration options
- [ ] Written a unit test if it works standalone, system.c especially
- [ ] Considered possible null pointers and out of bounds array indexing
- [ ] Changed no physics that affect existing maps
- [ ] Tested the change with [ASan+UBSan or valgrind's memcheck](https://github.com/ddnet/ddnet/#using-addresssanitizer--undefinedbehavioursanitizer-or-valgrinds-memcheck) (optional)


Co-authored-by: Jupeyy <jupjopjap@gmail.com>

src/game/editor/editor.cpp

@@ -3956,7 +3956,7 @@ void CEditor::RenderImages(CUIRect ToolBox, CUIRect View)
 
 	// render image
 	int i = m_SelectedImage;
-	if(i < m_Map.m_lImages.size())
+	if(i != -1 && i < m_Map.m_lImages.size())
 	{
 		CUIRect r;
 		View.Margin(10.0f, &r);