More fixes

This fixes the downloads of downloads and zipballs as well as this NPE:

java.lang.NullPointerException
at com.gh4a.activities.RepositoryActivity.onOptionsItemSelected(RepositoryActivity.java:405)
at android.support.v4.app.Watson.onMenuItemSelected(Watson.java:119)
at com.actionbarsherlock.ActionBarSherlock.callbackOptionsItemSelected(ActionBarSherlock.java:603)
at com.actionbarsherlock.internal.ActionBarSherlockNative.dispatchOptionsItemSelected(ActionBarSherlockNative.java:78)
at com.actionbarsherlock.app.SherlockFragmentActivity.onMenuItemSelected(SherlockFragmentActivity.java:205)
at com.android.internal.policy.impl.PhoneWindow.onMenuItemSelected(PhoneWindow.java:1012)
at com.android.internal.view.menu.MenuBuilder.dispatchMenuItemSelected(MenuBuilder.java:735)
at com.android.internal.view.menu.MenuItemImpl.invoke(MenuItemImpl.java:152)
[...]