Fix JS runtime exception on WebGL getContextAttributes (#25618)

[andvgal]

This is a blind fix for #25618

[juj]

How about

var t = c.GLctx?.getContextAttributes();
if (!t) return {{{ cDefs.EMSCRIPTEN_RESULT_INVALID_TARGET }}};

?

Although do note that if the GL context is lost, then all subsequent GL calls will fail as well. So if you have a code path that can somehow recover (if it is an iOS 26.1 internal bug, one might not exist), you will need to call emscripten_is_webgl_context_lost() or register to emscripten_set_webglcontextlost_callback() to be notified of a context loss, to do something else.

I.e. the issue will likely not be isolated to this function, but all subsequent GL operations will fail as well.

[andvgal]

First of all, that is a blind fix for a runtime exception. The fact that the context is not usable any more is out of scope.

The refactoring suggestion imposes another minimal ECMAScript version. I am not that familiar with the project and its application, but the code around suggests ES6-level of coding about when WebAssembly got first introduced. Optional chaining is ES2020.

[juj]

Emscripten project uses Babel to transpile to older ES standards. Using ?. is ok here.

[andvgal]

OK, then following your advice.