Fix init if devices directory does not exist/is empty

core/init.go

@@ -53,7 +53,7 @@ func GpgKeyGen() string {
 }
 
 // DirInit creates the libmutton directories.
-// Returns: oldDeviceID (from before the directory reset).
+// Returns: oldDeviceID (from before the directory reset; will be sync.FSMisc if there is no pre-existing ID).
 func DirInit(preserveOldConfigDir bool) string {
 	// create EntryRoot
 	err := os.MkdirAll(EntryRoot, 0700)
@@ -63,7 +63,13 @@ func DirInit(preserveOldConfigDir bool) string {
 	}
 
 	// get old device ID before its potential removal
-	oldDeviceID := (*GenDeviceIDList(false))[0].Name() // errorOnFail set to false to ignore error if device ID directory does not exist (error non-critical for this function)
+	oldDeviceIDList := GenDeviceIDList(false) // errorOnFail is false so that nil is received when the devices directory does not exist
+	var oldDeviceID string
+	if oldDeviceIDList != nil && len(*oldDeviceIDList) > 0 { // ensure not derferencing nil, which occurs when the devices directory does not exist
+		oldDeviceID = (*oldDeviceIDList)[0].Name()
+	} else {
+		oldDeviceID = "\u259f" // sync.FSMisc cannot be used directly due to import cycle; indicates to server that no device ID is being replaced
+	}
 
 	// remove existing config directory (if it exists and not in append mode)
 	if !preserveOldConfigDir {