improved last line handling

spells/menu/bitcoin/configure-bitcoin

@@ -44,7 +44,7 @@ fi
 modify_bitcoin_conf() {
     local key=$1
     local value=$2
-    awk -v key="$key" -v value="$value" 'BEGIN {found=0} !/^#/ && $1==key {found=1; print key"="value; next} {print} END {if (!found) print key"="value}' "$bitcoin_conf" > "$bitcoin_conf.tmp" && mv "$bitcoin_conf.tmp" "$bitcoin_conf" || retry_with_sudo mv "$bitcoin_conf.tmp" "$bitcoin_conf"
+    awk -v key="$key" -v value="$value" 'BEGIN {found=0} !/^#/ && $1==key {found=1; print key"="value; next} {print} END {if (!found) print key"="value; print ""}' "$bitcoin_conf" > "$bitcoin_conf.tmp" && mv "$bitcoin_conf.tmp" "$bitcoin_conf" || retry_with_sudo mv "$bitcoin_conf.tmp" "$bitcoin_conf"
 }
 
 # Pruning question and storage amount