Fix crash in developer settings when backup is not available

When backup feature is disabled, Developer Settings dialog does
not come up due to a crash.

Disable Backup Password option in the preference screen.

Bug: 64725174
Test: Developer settings dialog comes up and Backup password is
      disabled on Polaris

Change-Id: I4f4546c4e97d2e5128ec65c0532691d9799b4c8f

src/com/android/settings/development/DevelopmentSettings.java

@@ -892,6 +892,8 @@ public class DevelopmentSettings extends RestrictedSettingsFragment
     }
 
     private void updatePasswordSummary() {
+        mPassword.setEnabled(mBackupManager != null);
+        if (mBackupManager != null) {
             try {
                 if (mBackupManager.hasBackupPassword()) {
                     mPassword.setSummary(R.string.local_backup_password_summary_change);
@@ -902,6 +904,7 @@ public class DevelopmentSettings extends RestrictedSettingsFragment
                 // Not much we can do here
             }
         }
+    }
 
     private void writeBtHciSnoopLogOptions() {
         BluetoothAdapter adapter = BluetoothAdapter.getDefaultAdapter();