random tree growth can block building sites needed to progress in scenario

In the first Empire level of the campaign, a palm tree randomly grew on the spot of the southern small building site, preventing me from building a lumberjack's house there when prompted. The attached screenshot shows the stuck situation, with no free building sites.

Workarounds:
1. Disassemble the barracks and replace them with a lumberjack's house
2. Immediately build a second barracks there instead (the only available building type), blocking its resources, and replaced it with the lumberjack's house later

Neither workaround is ideal for a tutorial level.