droidvnc-ng.c: Changed default action in case of errors

Contrary to before, now, if some error occurs during address translation, it is reported, instead of using the 0.0.0.0 address.

app/src/main/cpp/droidvnc-ng.c

@@ -317,13 +317,18 @@ JNIEXPORT jboolean JNICALL Java_net_christianbeier_droidvnc_1ng_MainService_vncS
 
     in_addr_t address = 0; // Default is 0.0.0.0
     if (listenIf != NULL) {
-        const char *listenIfNative = (*env)->GetStringUTFChars(env, listenIf, NULL);
-        if (!rfbStringToAddr((char*)listenIfNative, &address)) {
-            address = 0; // If problems arise, assume 0.0.0.0
+        const char *cListenInterface = (*env)->GetStringUTFChars(env, listenIf, NULL);
+        int addrConvSucceded = rfbStringToAddr((char*)cListenInterface, &address);
+        (*env)->ReleaseStringUTFChars(env, listenIf, cListenInterface);
+
+        if (!addrConvSucceded) {
+            __android_log_print(ANDROID_LOG_ERROR, TAG, "vncStartServer: invalid listen address");
+            Java_net_christianbeier_droidvnc_1ng_MainService_vncStopServer(env, thiz);
+            return JNI_FALSE;
         }
-        (*env)->ReleaseStringUTFChars(env, listenIf, listenIfNative);
     }
 
+
     // With the listenInterface property one can define where the server will be available
     theScreen->listenInterface = address;
     theScreen->port = port;