[Fix] `nvm install`: Handle 'N/A' version instead of asking to install it
[Fix] `nvm install`: Handle 'N/A' version instead of asking to install it

Fixes #1304.

ljharb/nvm,PeterDaveHelloKitchen/nvm,evocateur/nvm,evocateur/nvm,PeterDaveHello/nvm,creationix/nvm,PeterDaveHelloKitchen/nvm,ljharb/nvm,creationix/nvm,PeterDaveHello/nvm,edwmurph/nvm,edwmurph/nvm