Ensured an exception is thrown if no machine to run a file is found. E.g. right now if you tried to open a ZX Spectrum .tap.

OSBindings/Mac/Clock Signal/Documents/MachineDocument.swift

@@ -120,6 +120,8 @@ class MachineDocument:
 		if let analyser = CSStaticAnalyser(fileAt: url) {
 			self.displayName = analyser.displayName
 			self.configureAs(analyser)
+		} else {
+			throw NSError(domain: "MachineDocument", code: -1, userInfo: nil)
 		}
 	}