Update language-inference-engine.js

- Add response type check before parsing
- Wrap JSON.parse in a try/catch to handle potential malformed responses.
- Use “system” role for the initial bias message on gemini model object's wrap

lib/language-inference-engine.js

@@ -196,9 +196,10 @@ var ENGINE_PROFILES = {
         },
         "url": "https://generativelanguage.googleapis.com/v1beta/models/{model}:generateContent?key={apikey}",
         "wrap": function(model, message, temperature) {
+            const BIAS_MESSAGE = BIAS_MESSAGE
             return {
                 "contents": [{
-                    "role": "user", // Changed "developer" to "user" for the initial prompt.  The overall prompt is still intended to guide the model, so this is reasonable.
+                    "role": "system",
                     "parts": [{
                         "text": BIAS_MESSAGE
                     }]
@@ -214,7 +215,6 @@ var ENGINE_PROFILES = {
             };
         },
         "callback": function(response) {
-            response = JSON.parse(response)
             if ("error" in response) {
                 return ["Error: " + response.error.message];
             } else {
@@ -531,6 +531,14 @@ function LanguageInferenceEngine() {
             .send()
             .responseBody;
 
+            if(typeof response === 'string'){
+                try {
+                    response = JSON.parse(response)
+                } catch (e) {
+                    return ["Error: Malformed response"];
+                }
+            }
+        
         return callback(response);
     };
 }