Fix scratchpad fullscreen behavior and crash

When setting fullscreen on a hidden scratchpad container, there was a
check to see if there was an existing fullscreen container on the
workspace so it could be fullscreen disabled first. Since the workspace
is NULL, it would cause a SIGSEGV. This adds a NULL check to avoid the
crash.

This also changes the behavior of how fullscreen is handled when adding
a container to the scratchpad or changing visibility of a scratchpad
container to match i3's. The behavior is as follows:
- When adding a container to the scratchpad or hiding a container back
  into the scratchpad, there is an implicit fullscreen disable
- When setting fullscreen on a container that is hidden in the
  scratchpad, it will be fullscreen when shown (and fullscreen disabled
  when hidden as stated above)
- When setting fullscreen global on a container that is hidden in the
  scratchpad, it will be shown immediately as fullscreen global. The
  container is not moved to a workspace and remains in the
  scratchpad. The container will be visible until fullscreen disabled
  or killed. Since the container is in the scratchpad, running
  `scratchpad show` or `move container to scratchpad` will have no
  effect

This also changes `container_replace` to transfer fullscreen and
scratchpad status.

sway/commands/floating.c

@@ -32,6 +32,11 @@ struct cmd_results *cmd_floating(int argc, char **argv) {
 		seat_set_focus_container(config->handler_context.seat, container);
 	}
 
+	if (container_is_scratchpad_hidden(container)) {
+		return cmd_results_new(CMD_INVALID,
+				"Can't change floating on hidden scratchpad container");
+	}
+
 	// If the container is in a floating split container,
 	// operate on the split container instead of the child.
 	if (container_is_floating_or_child(container)) {

sway/commands/focus.c

@@ -182,6 +182,10 @@ static struct sway_node *node_get_in_direction_floating(
 	double closest_distance = DBL_MAX;
 	struct sway_container *closest_con = NULL;
 
+	if (!con->workspace) {
+		return NULL;
+	}
+
 	for (int i = 0; i < con->workspace->floating->length; i++) {
 		struct sway_container *floater = con->workspace->floating->items[i];
 		if (floater == con) {

sway/commands/fullscreen.c

@@ -26,6 +26,13 @@ struct cmd_results *cmd_fullscreen(int argc, char **argv) {
 				"Can't fullscreen an empty workspace");
 	}
 
+	// If in the scratchpad, operate on the highest container
+	if (container && !container->workspace) {
+		while (container->parent) {
+			container = container->parent;
+		}
+	}
+
 	bool is_fullscreen = container &&
 		container->fullscreen_mode != FULLSCREEN_NONE;
 	bool global = false;

sway/commands/layout.c

@@ -147,7 +147,11 @@ struct cmd_results *cmd_layout(int argc, char **argv) {
 			workspace->layout = new_layout;
 			workspace_update_representation(workspace);
 		}
-		arrange_workspace(workspace);
+		if (root->fullscreen_global) {
+			arrange_root();
+		} else {
+			arrange_workspace(workspace);
+		}
 	}
 
 	return cmd_results_new(CMD_SUCCESS, NULL);

sway/commands/move.c

@@ -395,6 +395,11 @@ static struct cmd_results *cmd_move_container(int argc, char **argv) {
 		container = workspace_wrap_children(workspace);
 	}
 
+	if (container->fullscreen_mode == FULLSCREEN_GLOBAL) {
+		return cmd_results_new(CMD_FAILURE,
+				"Can't move fullscreen global container");
+	}
+
 	bool no_auto_back_and_forth = false;
 	while (strcasecmp(argv[0], "--no-auto-back-and-forth") == 0) {
 		no_auto_back_and_forth = true;
@@ -646,6 +651,10 @@ static struct cmd_results *cmd_move_workspace(int argc, char **argv) {
 	}
 
 	struct sway_workspace *workspace = config->handler_context.workspace;
+	if (!workspace) {
+		return cmd_results_new(CMD_FAILURE, "No workspace to move");
+	}
+
 	struct sway_output *old_output = workspace->output;
 	int center_x = workspace->width / 2 + workspace->x,
 		center_y = workspace->height / 2 + workspace->y;

sway/commands/split.c

@@ -13,7 +13,8 @@ static struct cmd_results *do_split(int layout) {
 	struct sway_container *con = config->handler_context.container;
 	struct sway_workspace *ws = config->handler_context.workspace;
 	if (con) {
-		if (container_is_scratchpad_hidden(con)) {
+		if (container_is_scratchpad_hidden(con) &&
+				con->fullscreen_mode != FULLSCREEN_GLOBAL) {
 			return cmd_results_new(CMD_FAILURE,
 					"Cannot split a hidden scratchpad container");
 		}