SipSharedPreferences: add missed SharedPreferences.Editor.apply().

Change-Id: I4aac9abcdf2aecf9dbdb6176bf6ef37262fb72f2
diff --git a/src/com/android/phone/sip/SipSharedPreferences.java b/src/com/android/phone/sip/SipSharedPreferences.java
index 7c628b4..8168972 100644
--- a/src/com/android/phone/sip/SipSharedPreferences.java
+++ b/src/com/android/phone/sip/SipSharedPreferences.java
@@ -42,7 +42,9 @@
     }
 
     public void setPrimaryAccount(String accountUri) {
-        mPreferences.edit().putString(KEY_PRIMARY_ACCOUNT, accountUri);
+        SharedPreferences.Editor editor = mPreferences.edit();
+        editor.putString(KEY_PRIMARY_ACCOUNT, accountUri);
+        editor.apply();
     }
 
     /** Returns the primary account URI or null if it does not exist. */