Fixes

-Fixed Expand_2 page missing in the table of contents and added a link from Expand_1. -Polyculture now actually starts at 5x like documented. -Fixed the displayed plant cost in entity tooltips. -Using a negative number of items now throws an error instead of giving you items. -Division by 0 now throws an error instead of returning NaN. -Fixed the invalid key error message of set.add(). -Indexing dicts with empty tuples is no longer free. -Fixed leaderboard UI blocking mouse clicks. -Resolved the issues that sometimes caused an older version of the code to execute. -Fixed a bug preventing the drone to move onto the end of the dinosaur tail one move after picking up an apple. -Fixed a bug that caused window sizes to stop snapping to the code after moving the window.