tools: Fix check-plugin-monorepo-deps.sh with no monorepo deps (#28324)

If there are no monorepo package deps, the script prints out an error
like

  crm:  should be at dev-trunk, not

That shouldn't happen, add a check for the situation to avoid it.

tools/check-plugin-monorepo-deps.sh

@@ -103,6 +103,7 @@ for PLUGIN in "${PLUGINS[@]}"; do
 
 	# Check lock file versions
 	TMP="$(composer info --locked --format=json --working-dir="$DIR" | jq -r --argjson packages "$PACKAGES" '.locked[] | select( $packages[.name] ) | [ .name, .version, $packages[.name].rel ] | @tsv')"
+	[[ -n "$TMP" ]] || continue
 	while IFS=$'\t' read -r PKG LOCKVER EXPECTVER; do
 		if [[ "$WHAT" == "dev" ]]; then
 			if [[ "$LOCKVER" != "dev-trunk" ]]; then