This fixes an initialization regression in 0.34.0 where users saw TypeError: Cannot read property 'done' of undefined instead of their actual initialization error, such as a tsconfig issue (such as with https://github.com/ezolenko/rollup-plugin-typescript2/issues/421)
0.34.0 introduced a type-only fix that relied on Rollup 2.60.0+ and would (accidentally) error out on older versions of Rollup. This fix handles it gracefully with a clear warning message instead and skips that check when using an older version of Rollup (i.e. partly backward-compatible).
