Merge branch 'jk/submodule-init-segv-fix'

Fix a segv in 'submodule init' when url is not given for a submodule.

* jk/submodule-init-segv-fix:
  submodule_init: die cleanly on submodules without url defined

diff --cc builtin/submodule--helper.c
Simple merge

diff --cc t/t7400-submodule-basic.sh
Simple merge