installer: Don't attempt to use nil ssh agent
installer: Don't attempt to use nil ssh agent

Signed-off-by: Jesse Stuart <a5c95b3d7cb4d0ae05a15c79c79ab458dc2c8f9e@jessestuart.ca>

flynn/flynn,philiplb/flynn,lmars/flynn,flynn/flynn,lmars/flynn,philiplb/flynn,flynn/flynn,philiplb/flynn,benbjohnson/flynn,philiplb/flynn,flynn/flynn,benbjohnson/flynn,benbjohnson/flynn,lmars/flynn,flynn/flynn,benbjohnson/flynn,benbjohnson/flynn,philiplb/flynn,lmars/flynn,benbjohnson/flynn,lmars/flynn