status: Prevent segfaulting when determining the status of a repository

Fixes #465

src/status.c

@@ -183,8 +183,9 @@ static int process_folder(struct status_st *st, const git_tree_entry *tree_entry
 	git_object *subtree = NULL;
 	git_tree *pushed_tree = NULL;
 	int error, pushed_tree_position = 0;
-	git_otype tree_entry_type;
+	git_otype tree_entry_type = GIT_OBJ_BAD;
 
+	if (tree_entry != NULL) {
 		tree_entry_type = git_tree_entry_type(tree_entry);
 
 		switch (tree_entry_type) {
@@ -204,6 +205,7 @@ static int process_folder(struct status_st *st, const git_tree_entry *tree_entry
 		default:
 			error = git__throw(GIT_EINVALIDTYPE, "Unexpected tree entry type");	/* TODO: How should we deal with submodules? */
 		}
+	}
 
 	if (full_path != NULL && path_type == GIT_STATUS_PATH_FOLDER)
 		error = alphasorted_futils_direach(full_path, GIT_PATH_MAX, dirent_cb, st);