fix(www): handle case when gatsbyMajorVersion is unset in a starter

[jamo]

Seems to fix:

21:36:45 PM: error Building static HTML failed for path "/starters/"
21:36:45 PM: 104 | </span> 105 | <span css={{ display: `flex` }}> > 106 | {gatsbyMajorVersion[0][1] === `2` && ( | ^ 107 | <span 108 | sx={{ 109 | alignItems: `center`, WebpackError: TypeError: Cannot read property '1' of undefined - starter-list.js:106 StartersList.starters.map src/views/starter-library/starter-list.js:106:46 - starter-list.js:63 StartersList src/views/starter-library/starter-list.js:63:19
21:36:46 PM: ERROR Failed to compile: Error: Exited with code 1

Not sure if there is a nicer way to fix this in the query 🙈

[pieh]

Thanks!