Teapot causes a crash and freeze

[KatieWoe]

Test device:
Dell Laptop
Operating System:
Win 10
Browser:
firefox (reproduced on chrome)
Problem description:
For phetsims/qa#258
It is possible for the sim to crash and freeze when the teapot is used under certain circumstances.
Steps to reproduce:

1. Go to the second screen
2. Select teapot and solar panel
3. Make sure energy chunks are off
4. Heat teapot and keep heated
5. Wait until steam cloud is large
6. Select Energy chunks. Sim will freeze at this point

Screenshots:

Troubleshooting information (do not edit):

Name: ‪Energy Forms And Changes‬
URL: https://phet-dev.colorado.edu/html/energy-forms-and-changes/1.0.0-dev.15/phet/energy-forms-and-changes_en_phet.html
Version: 1.0.0-dev.15 2019-01-15 20:46:49 UTC
Flags: pixelRatioScaling
User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:64.0) Gecko/20100101 Firefox/64.0
Language: en-US
Window: 1536x760
Pixel Ratio: 2.5/1
WebGL: WebGL 1.0
GLSL: WebGL GLSL ES 1.0
Vendor: Mozilla (Mozilla)
Vertex: attribs: 16 varying: 30 uniform: 4096
Texture: size: 16384 imageUnits: 16 (vertex: 16, combined: 32)
Max viewport: 32767x32767
OES_texture_float: true
Dependencies JSON: {}

[chrisklus]

Nice find @KatieWoe! I can reproduce on my Macbook Pro as well, both Chrome and Firefox.

[chrisklus]

There was no handling in preloadEnergyChunks for the case when the tea kettle has no system to give its energy chunks to, so the freeze was caused by the sim being stuck in a while loop. When the tea kettle is hooked up to the generator, the chunks that don't get selected for transfer get put into an exemptFromTransferEnergyChunks array, so I pushed the preloading chunks into there as well when they have no next system to go to.

This fixed the bug, but there is a bit of a gap between the preloaded energy chunks and the following chunks that come out of the burner once symbols are on because of the way preloadEnergyChunks was implemented. Fixing this gap is low priority, so I've created a second issue for it, see #178

@KatieWoe could you test on your device and confirm this is working?

[KatieWoe]

Looks good @chrisklus

[chrisklus]

Sweet, thanks. Closing.