Backup charging sounds enabled toggle correctly

Previously deprecated global settings property was overriding
the secure setting for charging_sounds_enabled. Only use the
global setting if the secure setting is unset (null).

Test: manual (repeat steps from bug)
Change-Id: I0bceab765764662855a053c82cb7251a14d4a1d8
Fixes: 119761984

packages/SettingsProvider/src/com/android/providers/settings/SettingsProvider.java

@@ -4125,10 +4125,12 @@ public class SettingsProvider extends ContentProvider {
                             Secure.CHARGING_SOUNDS_ENABLED);
 
                     if (!globalChargingSoundEnabled.isNull()) {
-                        secureSettings.insertSettingLocked(
-                                Secure.CHARGING_SOUNDS_ENABLED,
-                                globalChargingSoundEnabled.getValue(), null, false,
-                                SettingsState.SYSTEM_PACKAGE_NAME);
+                        if (secureChargingSoundsEnabled.isNull()) {
+                            secureSettings.insertSettingLocked(
+                                    Secure.CHARGING_SOUNDS_ENABLED,
+                                    globalChargingSoundEnabled.getValue(), null, false,
+                                    SettingsState.SYSTEM_PACKAGE_NAME);
+                        }
 
                         // set global charging_sounds_enabled setting to null since it's deprecated
                         globalSettings.insertSettingLocked(