Remove empty lines from the current_state file after redirecting the …

…update_available var value to it

When there are no update available, redirecting the value of the update_available var (which is then empty) to the file produces an empty (but existing) line.
This commit aims to remove it so the file is actually empty (instead of containing an empty/blank line).

src/script/arch-update.sh

@@ -316,6 +316,7 @@ check() {
 		fi
 
 		echo "${update_available}" > "${statedir}/current_check"
+		sed -i '/^\s*$/d' "${statedir}/current_check"
 	fi
 
 	if [ -n "${update_available}" ]; then