install: some tweaks and clean-up

install.sh

@@ -133,14 +133,14 @@ nvm_check_global_modules() {
   [ "${NPM_VERSION%%[!0-9]*}" -gt 1 ] || return 0
 
   local NPM_GLOBAL_MODULES
-  NPM_GLOBAL_MODULES=$(npm list -g --depth=0 | sed '/ npm@/d')
+  NPM_GLOBAL_MODULES="$(npm list -g --depth=0 | sed '/ npm@/d')"
 
   local MODULE_COUNT
-  MODULE_COUNT=$(
+  MODULE_COUNT="$(
     printf %s\\n "$NPM_GLOBAL_MODULES" |
     sed -ne '1!p' |                             # Remove the first line
     wc -l | tr -d ' '                           # Count entries
-  )
+  )"
 
   if [ $MODULE_COUNT -ne 0 ]; then
     cat <<-'END_MESSAGE'

test/install_script/nvm_check_global_modules

@@ -25,11 +25,11 @@ setup () {
 
 setup
 
-npm install -g nop >/dev/null 2>&1
+npm install -g nop >/dev/null
 message=$(nvm_check_global_modules)
 [ ! -z "$message" ] || die "nvm_check_global_modules should have printed a notice when npm had global modules installed"
 
-npm uninstall -g nop >/dev/null 2>&1
+npm uninstall -g nop >/dev/null
 message=$(nvm_check_global_modules)
 [ -z "$message" ] || die "nvm_check_global_modules should not have printed a notice when npm had no global modules installed"