Fix 2520977: NPE in com.android.settings.deviceinfo.Status

In normal operation, Phone.getLine1Number() returns an empty string if the
device doesn't know its own phone number for some reason.  However the
monkey caught a case where it was returning null, which crashed the
Settings -> About Phone -> Status app.

However the javadoc for Phone.getLine1Number() *does* clearly say "May
return null if not available or the SIM is not ready", so the Status app
*should* gracefully handle this.

Now it does.  (We display this case as "Unknown", just like if we get an
empty string.)

FWIW I grepped thru the rest of the code base for other uses of
getLine1Number(), and everybody else *does* handle null gracefully except
for one case in apps/Mms, which I'll open a separate bug about.

Bug: 2520977
Change-Id: I173561f903f116dbdc2b7c32b8011b59a9eb29d7

src/com/android/settings/deviceinfo/Status.java

@@ -222,7 +222,13 @@ public class Status extends PreferenceActivity {
             }
         }
 
-        setSummaryText("number", PhoneNumberUtils.formatNumber(mPhone.getLine1Number()));
+        String rawNumber = mPhone.getLine1Number();  // may be null or empty
+        String formattedNumber = null;
+        if (!TextUtils.isEmpty(rawNumber)) {
+            formattedNumber = PhoneNumberUtils.formatNumber(rawNumber);
+        }
+        // If formattedNumber is null or empty, it'll display as "Unknown".
+        setSummaryText("number", formattedNumber);
 
         mPhoneStateReceiver = new PhoneStateIntentReceiver(this, mHandler);
         mPhoneStateReceiver.notifySignalStrength(EVENT_SIGNAL_STRENGTH_CHANGED);