Check return values from FindNode for null pointers

[cassiebeckley]

Fixes #227

[chaoticbob]

Looks good overall, just one small change.

[spencer-lunarg]

this is not a valid SPIR-V if using spirv-val

seems it has GLSL.std.453

after I see

%21 = OpAccessChain %20 %_ %19

[cassiebeckley]

Yeah, this is invalid, I included it specifically as a regression test since it triggers the null pointer dereference. I suspect any SPIR-V that triggers the error will be invalid, since it requires a reference to a node that doesn't exist.

This SPIR-V file is the one that was included in the original report of this issue; I suspect the reporter generated it using a fuzzer. I can try to clean it up more if you think that would be better.

I mention the issues with this file in README.md.

[spencer-lunarg]

That is fair

[cassiebeckley]

Looks good overall, just one small change.

@chaoticbob what did you want me to change? I don't think it's showing up for me.

[chaoticbob]

Looks good overall, just one small change.

@chaoticbob what did you want me to change? I don't think it's showing up for me.

One of the comments was to add parens around the right hand side of a logical expressions.

[cassiebeckley]

Okay, fixed that. Anything else?

[chaoticbob]

LGTM