Fix handling sync server errors

app/src/main/java/org/koitharu/kotatsu/utils/ext/HttpExt.kt

@@ -3,8 +3,9 @@ package org.koitharu.kotatsu.utils.ext
 import okhttp3.MediaType.Companion.toMediaType
 import okhttp3.RequestBody.Companion.toRequestBody
 import okhttp3.Response
+import okhttp3.internal.closeQuietly
+import okio.IOException
 import org.json.JSONObject
-import org.koitharu.kotatsu.parsers.util.parseJson
 import java.net.HttpURLConnection
 
 private val TYPE_JSON = "application/json".toMediaType()
@@ -12,9 +13,13 @@ private val TYPE_JSON = "application/json".toMediaType()
 fun JSONObject.toRequestBody() = toString().toRequestBody(TYPE_JSON)
 
 fun Response.parseJsonOrNull(): JSONObject? {
-	return if (code == HttpURLConnection.HTTP_NO_CONTENT) {
+	return try {
-		null
+		when {
-	} else {
+			!isSuccessful -> throw IOException(body?.string())
-		parseJson()
+			code == HttpURLConnection.HTTP_NO_CONTENT -> null
+			else -> JSONObject(body?.string() ?: return null)
+		}
+	} finally {
+		closeQuietly()
 	}
 }