At some point in your process you have to create the "MyImage" entity. It looks like it should have an association to "RepairTicket". You could eliminate this by having "RepairTicket" inherit from System.Image, or you can fix it by auto creating the "MyImage" entity when you create a ticket, or the "Upload Image" link can be a microflow where you (retrieve or) create the "MyImage". Just remember if you're doing this with microflow in your create object action you must set the association and depending on where you're doing all of these things a "refresh in client" may be necessary.