Calling `compressedTexSubImage2D` without a prior `compressedTexImage2D`
for the same texture target and level caused the panic at
`tex_image_2d.rs:633` because `image_info_for_target` returned `None`
and `.unwrap()` was called on it.
Per the WebGL spec, this should generate `GL_INVALID_OPERATION` instead
of panicking. So this PR replaces the unwrap with proper error handling.
And also includes a WPT crash test that reproduces the original panic.
Fixes#43527
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Signed-off-by: thebabalola <t.babalolajoseph@gmail.com>