That is odd. Do you think you could try to run it as a debug build (you have it set to a release build right now) and see if you can get some more information about what is causing the crash?
I am also getting an error such as this. No matter how small I make the graph, it crashes on WebGL at the first attempted scan with a memory out of bounds exception.
edit: Also to be clear this does not come up as an issue in the Unity player. This issue only occurs running the WebGL build in a browser.
edit #2: I have commented out the lines where I call AstarPath.active.Scan(), and the error does not occur. I only get the trace shown above when a scan occurs.
I have upgraded to the newest version of the package. I still get a similar error (although it seems to my untrained eye to have a more detailed trace e.g. AddDirtyNode is now in the trace)
I managed to replicate this.
The problem was that the code relied on an exception being thrown, which is not possible when compiling with IL2CPP with exception support disabled.
The fix will be included in the next version.