Set NVM_IOJS to false by default to fix unbound variable error

[Deco]

When calling nvm run from a bash script that has "Treat unset variables as an error when substituting." set using set -u, it triggers an unbound variable error:

Found '/home/user/path/.nvmrc' with version <23.11.1>
/home/user/.nvm/nvm.sh: line 4017: NVM_IOJS: unbound variable

Setting the variable to false by default fixes this issue.

Test:

minimal_test_for_nvm_bug() {
    export NVM_DIR="$HOME/.nvm"
    [ -s "$NVM_DIR/nvm.sh" ] && \. "$NVM_DIR/nvm.sh"
    echo "23.11.1" > .nvmrc
    set -u
    nvm run node -e 'console.log("NVM Test Successful")'
}

minimal_test_for_nvm_bug

Notes: Tests not run. No AI used in this PR (except for AI line-completion while editing, which surely everyone uses by now).

[ljharb]

Suggested change

	local NVM_IOJS=false
	local NVM_IOJS
	NVM_IOJS=false

this is necessary for ksh, which doesn't support local

[Deco]

Thank you very much for the suggestion, @ljharb .

I don't have time to rebase and retest this pull request (which I know is part of the contribution requirements), so I'm just going to close it.

Also, the issue can be worked around by wrapping the call to nvm with set +u and set -u.

Sorry for the noise.