Update SettingsGeneralActivity.java

Possible Fix for crashing when Opening the general Settings after changing back the Unit setting.

Victor could you please check if this correct?

Should the OsmAnd/src/net/osmand/plus/OsmandSettings.java be changed too?

@@ -638,7 +639,7 @@ protected boolean setValue(Object prefs, DrivingRegion val) {
  	// this value string is synchronized with settings_pref.xml preference name
  	// cache of metrics constants as they are used very often
  	public final OsmandPreference<MetricsConstants> METRIC_SYSTEM = new EnumIntPreference<MetricsConstants>(
 -			"default_metric_system", MetricsConstants.KILOMETERS_AND_METERS, MetricsConstants.values()){
 +			"default_metric_system_new", MetricsConstants.KILOMETERS_AND_METERS, MetricsConstants.values()){
  		protected MetricsConstants getDefaultValue() {
  			return DRIVING_REGION.get().defMetrics;
  		};

https://github.com/osmandapp/Osmand/commit/2ef5d3442b8e36119f8b7366d2659f92f03848e2