Fix for concurrentmodificationexception on race condition.

src/org/thoughtcrime/securesms/service/MmsDownloader.java

@@ -138,25 +138,29 @@ public class MmsDownloader extends MmscProcessor {
   }
 
   protected void handleConnectivityChange() {
-    if (!isConnected()) {
-      if (!isConnectivityPossible() && !pendingMessages.isEmpty()) {
-        DatabaseFactory.getMmsDatabase(context).markDownloadState(pendingMessages.remove().getMessageId(), MmsDatabase.Types.DOWNLOAD_NO_CONNECTIVITY);
-        toastHandler.makeToast(context
-            .getString(R.string.MmsDownloader_no_connectivity_available_for_mms_download_try_again_later));
-        Log.w("MmsDownloadService", "Unable to download MMS, please try again later.");
-        finishConnectivity();
-      }
+    LinkedList<DownloadItem> downloadItems = (LinkedList<DownloadItem>)pendingMessages.clone();
 
-      return;
-    }
+    if (isConnected()) {
+      pendingMessages.clear();
 
-    for (DownloadItem item : pendingMessages) {
+      for (DownloadItem item : downloadItems) {
         downloadMms(item);
       }
 
+      finishConnectivity();
+    } else if (!isConnected() && !isConnectivityPossible()) {
       pendingMessages.clear();
+
+      for (DownloadItem item : downloadItems) {
+        DatabaseFactory.getMmsDatabase(context).markDownloadState(item.getMessageId(), MmsDatabase.Types.DOWNLOAD_NO_CONNECTIVITY);
+      }
+
+      toastHandler.makeToast(context
+          .getString(R.string.MmsDownloader_no_connectivity_available_for_mms_download_try_again_later));
+
       finishConnectivity();
     }
+  }
 
 
   private void scheduleDownloadWithRadioMode(DownloadItem item) {