Fix const function-parameter assertion discovered by fuzzer.

During constant-folding, we baked in an assertion stating that any
const-typed variable reference ought to have an initial value, because
you can't declare a const variable without assigning a value. However,
function parameters are an exception to this rule! They are variable
references and are allowed to be const, but will not have an initial
value. (In this case, `const` just means you can't alter the value.)

In this case, all we needed to do was remove the assertion; we already
treated this case defensively and with the appropriate care.

Change-Id: I61242c6d08c59886c6992898f195771e6334f2b4
Bug: oss-fuzz:37465
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/441239
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
7 files changed