Reset fish shell status even if variable not exists

[soraxas]

This is pretty straightforward, where it avoids polluting shell status with status code > 0.

Currently all the following functions activate, deactivate, reactivate, install, ... return non-zero status for me due to the variable setting in functions like

...
set -e CONDA_PREFIX
set -e CONDA_DEFAULT_ENV
set -e CONDA_PROMPT_MODIFIER
set -gx CONDA_SHLVL "0"

will return non-zero status if those variables do not exists.

Note1: set -e XXX can't erase non-existing variable, and will return non-zero status if that happens.

Note2: setting variable (e.g. set -gx CONDA_SHLVL "0") does not modify the current return status, so it doesn't reset the fail status from attempting to erase non-existing variables.

---

This just modify the erasing command into something like:

set -e CONDA_PREFIX || true
set -e CONDA_DEFAULT_ENV || true
set -e CONDA_PROMPT_MODIFIER || true
set -gx CONDA_SHLVL "0"

[jonashaag]

Thanks!