Why is this causing my app to crash?

I'm developing an app for my watch and have a list of different classes (referred to as 'courses' to avoid confusion) that I take in school, eg:

struct Course {
    let name: String
    let icon: String
    let room: String
    let colour: String
    
    let listName: String
    let listIcon: String
    
    init(name: String, icon: String, room: String? = nil, colour: String,
         listName: String? = nil, listIcon: String? = nil)
    {
        
        self.name = name
        self.icon = icon
        self.room = room ?? "None"
        self.colour = colour
        
        self.listName = listName ?? name
        self.listIcon = listIcon ?? icon+".circle.fill"
    }
    
    
}

// here's a few of my Course variables (there are lots more I've excluded)
let MathsCourse = Course(name: "Maths", icon: "number", room: "FT5", colour: "Rose")
let English6 = Course(name: "English", icon: "book.closed", room: "BT6", colour: "Lemon")
let LunchPeriod = Course(name: "Lunch", icon: "fork.knife", room: "food", colour: "White")

and I have designed a 'list view' of all the courses I have on whatever day it is. I used to define a different View for every course I defined but I merged the list data with the overall Course and replaced the Views with something that I should be able to call repeatedly and pass in a course to use, but unfortunately it's not working. (yes, I'm making a timetable app)

This is the template for a 'list view' for a class:

struct courseListView: View {
    var localcourse: Course
    var localtime: String
    
    var body: some View {
        HStack{
            
            Image(systemName: localcourse.listIcon)
                .foregroundColor(Color(localcourse.colour))
                .padding(.leading, 5)
            
            Text(localcourse.name)
                .bold()
            
            Spacer()
            
            Text(localtime)
            Text(roomOrBlank(course: localcourse)).bold().padding(.trailing, 5)
            
        }
        .padding(.bottom, 1)
        .background(currentCourse.name==localcourse.name ? Color(localcourse.colour).colorInvert(): nil)
    }
}

Then I should be able to programmatically work out what courses I have that day (I haven't scripted that bit yet), and compose a view containing all the courses:

struct ListView: View {
    var body: some View {
        ScrollView {
            VStack(alignment: .leading) {

                courseListView(localcourse: MathsCourse, localtime: "10:00")
                // ^^^ note above line; I'll come back to this

                // the idea is I can repeat that for a bunch of courses:
                courseListView(localcourse: English6, localtime: "11:00")
                courseListView(localcourse: LunchPeriod, localtime: "12:00")
            }
        }
    }
}

Then be able to call all that in my @main:

@main

struct Timetaber_Watch_AppApp: App {
    var body: some Scene {
        
        WindowGroup {
            TabView{
                HomeView()
                ListView()
                SettingsView()
            }
            .tabViewStyle(.carousel)
            .onAppear() {
                log()
            }
        }
        
    }
}

Unfortunately, each time I try to get a list view for a course,

// if you need a reminder:
courseListView(localcourse: MathsCourse, localtime: "10:00")

...even only calling it once causes my entire app to crash.

Here's an excerpt from the crash report:

Exception Type:  EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000001, 0x0000000180210194
Termination Reason: SIGNAL 5 Trace/BPT trap: 5
Terminating Process: exc handler [14932]

Triggered by Thread:  0

Thread 0 Crashed::  Dispatch queue: com.apple.main-thread
0   libdispatch.dylib             	       0x180210194 _dispatch_once_wait.cold.1 + 28
1   libdispatch.dylib             	       0x1801db4f4 _dispatch_once_wait + 184
2   ???                           	       0x3400200d0 ???
3   ???                           	       0x340020198 ???
4 ...

So...
Anyone know what's happening?