fix crash when UpdateService receives null Intent

IntentServices can get a null Intent if they are restarted after being
killed.  So this should be properly handled.

"[The intent] may be null if the service is being restarted after its
process has gone away, and it had previously returned anything except
START_STICKY_COMPATIBILITY."
https://developer.android.com/reference/android/app/IntentService.html#onStartCommand(android.content.Intent,%20int,%20int)

ANDROID_VERSION=5.1.1
APP_VERSION_NAME=0.99.2
BRAND=samsung
PHONE_MODEL=SM-G901F
java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Intent.getStringExtra(java.lang.String)' on a null object reference
	at org.fdroid.fdroid.UpdateService.onHandleIntent(UpdateService.java:342)
	at android.app.IntentService$ServiceHandler.handleMessage(IntentService.java:65)
	at android.os.Handler.dispatchMessage(Handler.java:102)
	at android.os.Looper.loop(Looper.java:135)
	at android.os.HandlerThread.run(HandlerThread.java:61)

app/src/main/java/org/fdroid/fdroid/CleanCacheService.java

@@ -47,6 +47,9 @@ public class CleanCacheService extends IntentService {
 
     @Override
     protected void onHandleIntent(Intent intent) {
+        if (intent == null) {
+            return;
+        }
         Process.setThreadPriority(Process.THREAD_PRIORITY_LOWEST);
         Utils.clearOldFiles(Utils.getApkCacheDir(this), Preferences.get().getKeepCacheTime());
         deleteStrayIndexFiles();

app/src/main/java/org/fdroid/fdroid/UpdateService.java

@@ -313,8 +313,12 @@ public class UpdateService extends IntentService {
         Process.setThreadPriority(Process.THREAD_PRIORITY_LOWEST);
 
         final long startTime = System.currentTimeMillis();
-        String address = intent.getStringExtra(EXTRA_ADDRESS);
+        boolean manualUpdate = false;
-        boolean manualUpdate = intent.getBooleanExtra(EXTRA_MANUAL_UPDATE, false);
+        String address = null;
+        if (intent != null) {
+            address = intent.getStringExtra(EXTRA_ADDRESS);
+            manualUpdate = intent.getBooleanExtra(EXTRA_MANUAL_UPDATE, false);
+        }
 
         try {
             // See if it's time to actually do anything yet...

app/src/main/java/org/fdroid/fdroid/net/DownloaderService.java

@@ -33,7 +33,6 @@ import android.os.Process;
 import android.support.v4.content.IntentCompat;
 import android.support.v4.content.LocalBroadcastManager;
 import android.text.TextUtils;
-import android.util.Log;
 
 import org.fdroid.fdroid.ProgressListener;
 import org.fdroid.fdroid.Utils;
@@ -46,9 +45,14 @@ import java.net.URL;
 /**
  * DownloaderService is a service that handles asynchronous download requests
  * (expressed as {@link Intent}s) on demand.  Clients send download requests
- * through {@link android.content.Context#startService(Intent)} calls; the
+ * through {@link #queue(Context, String)} calls.  The
- * service is started as needed, handles each Intent in turn using a worker
+ * service is started as needed, it handles each {@code Intent} using a worker
- * thread, and stops itself when it runs out of work.
+ * thread, and stops itself when it runs out of work.  Requests can be canceled
+ * using {@link #cancel(Context, String)}.  If this service is killed during
+ * operation, it will receive the queued {@link #queue(Context, String)} and
+ * {@link #cancel(Context, String)} requests again due to
+ * {@link Service#START_REDELIVER_INTENT}.  Bad requests will be ignored,
+ * including on restart after killing via {@link Service#START_NOT_STICKY}.
  * <p>
  * This "work queue processor" pattern is commonly used to offload tasks
  * from an application's main thread.  The DownloaderService class exists to
@@ -112,10 +116,15 @@ public class DownloaderService extends Service {
     @Override
     public int onStartCommand(Intent intent, int flags, int startId) {
         Utils.debugLog(TAG, "Received Intent for downloading: " + intent + " (with a startId of " + startId + ")");
+
+        if (intent == null) {
+            return START_NOT_STICKY;
+        }
+
         String uriString = intent.getDataString();
         if (uriString == null) {
-            Log.e(TAG, "Received Intent with no URI: " + intent);
+            Utils.debugLog(TAG, "Received Intent with no URI: " + intent);
-            return START_STICKY;
+            return START_NOT_STICKY;
         }
 
         if (ACTION_CANCEL.equals(intent.getAction())) {
@@ -128,7 +137,7 @@ public class DownloaderService extends Service {
             } else if (isActive(uriString)) {
                 downloader.cancelDownload();
             } else {
-                Log.e(TAG, "ACTION_CANCEL called on something not queued or running (expected to find message with ID of " + whatToRemove + " in queue).");
+                Utils.debugLog(TAG, "ACTION_CANCEL called on something not queued or running (expected to find message with ID of " + whatToRemove + " in queue).");
             }
         } else if (ACTION_QUEUE.equals(intent.getAction())) {
             Message msg = serviceHandler.obtainMessage();
@@ -138,7 +147,7 @@ public class DownloaderService extends Service {
             serviceHandler.sendMessage(msg);
             Utils.debugLog(TAG, "Queued download of " + uriString);
         } else {
-            Log.e(TAG, "Received Intent with unknown action: " + intent);
+            Utils.debugLog(TAG, "Received Intent with unknown action: " + intent);
         }
 
         return START_REDELIVER_INTENT; // if killed before completion, retry Intent