settings: fix migrate routine never working with empty settings

code/espurna/migrate.cpp

@@ -27,13 +27,23 @@ void _cmpMoveIndexDown(const char * key, int offset = 0) {
 // 3: based on Embedis, with board definitions 0-based
 // 4: based on Embedis, no board definitions
 
+int migrateVersion() {
+    const static auto version = getSetting("cfg", CFG_VERSION);
+    if (version == CFG_VERSION) {
+        return 0;
+    }
+
+    return version;
+}
+
 void migrate() {
 
     // Update if not on the latest version
-    const auto version = getSetting("cfg", CFG_VERSION);
-    if (version == CFG_VERSION) return;
+    const auto version = migrateVersion();
     setSetting("cfg", CFG_VERSION);
 
+    if (!version) return;
+
     switch (version) {
         // migrate old version with 1-based indices
         case 2:

code/espurna/settings.h

@@ -225,9 +225,15 @@ void settingsProcessConfig(const settings_cfg_list_t& config, settings_filter_t
 
 size_t settingsSize();
 
-void migrate();
 void settingsSetup();
 
+// -----------------------------------------------------------------------------
+// Configuration updates
+// -----------------------------------------------------------------------------
+
+int migrateVersion();
+void migrate();
+
 // -----------------------------------------------------------------------------
 // Deprecated implementation
 // -----------------------------------------------------------------------------