[class] Prevent lebab from crashing when using anonymous function declaration on default export

[uniibu]

Fixes a bug on Lebab where in it throws a SyntaxError when class transform is enabled and the user is using anonymous function declaration on default export.

example:

export default function() {}

• will throw SyntaxError Cannot read property 'name' of null when class transform is enabled

[codecov-io]

Codecov Report

Merging #289 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #289   +/-   ##
=======================================
  Coverage   99.56%   99.56%           
=======================================
  Files          83       83           
  Lines        1145     1145           
=======================================
  Hits         1140     1140           
  Misses          5        5

Impacted Files	Coverage Δ
src/transform/class/matchFunctionDeclaration.js	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 35f94e1...fef54d9. Read the comment docs.

[nene]

Thanks!

[nene]

Published as 3.0.5.