fix: phin handle 400 empty body

phin doesn't throw on 400 and instead passes empty body to tg

package.json

@@ -1,6 +1,6 @@
 {
   "name": "ussd-tg-proxy",
-  "version": "0.3.0",
+  "version": "0.3.1",
   "description": "ussd-tg-proxy",
   "main": "src/index.js",
   "repository": "https://git.grassecon.net/grassrootseconomics/ussd-tg-proxy.git",

src/request.js

@@ -21,7 +21,10 @@ async function proxy(sessionId, phone, input = "") {
   try {
     const { body } = await phin(requestOptions);
     log.debug({ body: body }, "response body");
-    return body;
+    if (body.length > 1) {
+      return body;
+    }
+    throw new Error("empty body");
   } catch (error) {
     log.error(error);
     return "ERR Something went wrong, try again later.";