Better error handling in CorpusAnalysisApp

app/static/js/cqi/api/client.js

@@ -30,7 +30,11 @@ cqi.api.APIClient = class APIClient {
     } else if (response.code === 500) {
       throw new Error(`[${response.code}] ${response.msg}`);
     } else if (response.code === 502) {
-      throw new cqi.errors.lookup[response.payload.code]();
+      if (response.payload.code in cqi.errors.lookup) {
+        throw new cqi.errors.lookup[response.payload.code]();
+      } else {
+        throw new cqi.errors.CQiError();
+      }
     }
   }