While blitting, it's possible to generate a float that is outside the
representable values of an integer. Since converting such a float
results in undefined behavior, we instead throw an invalid operation
error and return without continuing the blit.

Bug chromium:1001874

Change-Id: Ic6938adf75176e34021d0ca1404176e4979a3ca6
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/36408Reviewed-by: Alexis Hétu <sugoi@google.com>
Tested-by: Sean Risser <srisser@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>