Found it when trying to add a repo manually:
E/AndroidRuntime(30549): java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.replaceAll(java.lang.String, java.lang.String)' on a null object reference
E/AndroidRuntime(30549): at org.fdroid.fdroid.views.ManageReposActivity$AddRepo.normalizeUrl(ManageReposActivity.java:547)
E/AndroidRuntime(30549): at org.fdroid.fdroid.views.ManageReposActivity$AddRepo.validateRepoDetails(ManageReposActivity.java:358)
E/AndroidRuntime(30549): at org.fdroid.fdroid.views.ManageReposActivity$AddRepo.access$700(ManageReposActivity.java:218)
E/AndroidRuntime(30549): at org.fdroid.fdroid.views.ManageReposActivity$AddRepo$4.afterTextChanged(ManageReposActivity.java:342)
E/AndroidRuntime(30549): at android.widget.TextView.sendAfterTextChanged(TextView.java:7698)