Steps to reproduce:
1. Open attached project "stripped_webgl.zip"
2. Add "Main" scene to build settings and build for WebGL
3. Run built player with a browser with WebGL support (used Firefox for testing)
Result: app fails to run and outputs a Javascript error:

An error occured running the Unity content on this page. See your browser's JavaScript console for more info. The error was:
uncaught exception: abort(-1) at jsStackTrace@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:1:22715
stackTrace@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:1:22898
abort@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:53:61047
_Initialize@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:1:310631
W4y@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:12:1
V_F@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:43:1
wUo@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:19:1
O7j@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:6:1
eyP@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:46:1
invoke_iiii@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:1:384940
bsF@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:35:1
GrF@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:35:1
XPa@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:29:1
_cb@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:29:1
zab@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:29:1
Bab@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:29:1
hab@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:29:1
Cva@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:25:1
c7a@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:29:1
Dhc@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:18:1
yxP@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:46:1
Runtime.dynCall@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:1:6786
Browser_mainLoop_runner/<@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:1:210888
Browser.mainLoop.runIter@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:1:241727
Browser_mainLoop_runner@blob:null/8c751c9d-d478-4d2e-97c2-68e2caae6632:1:210784

If this abort() is unexpected, build with -s ASSERTIONS=1 which can give more information.

Reproduced with: 5.4.1p2, 5.4.3p3

Not reproducible with: 5.4.1p1

Regression Introduced in 5.4.1p2