This is a minor patch with the following game crash fixes:

• Level 'Convoy' blocker - Uncaught TypeError: Cannot use 'in' operator to search for 'spawn-rate-percent' in 5 (thanks to juan ignacio)
• Custom levels with no builder units - Uncaught TypeError: Cannot read property 'onMatterChange' of undefined
• Rare Experiments bug - Uncaught TypeError: Cannot read property 'wavesGrp' of null (kudos to Kubla Khan)
• Rare Level Editor issue - Uncaught TypeError: Cannot read property 'properties' of null

We also added some annoying help tips in Level Editor.