Avoid parsing an http body error if response is not from Ably.

Author: maratal

Source/ARTRest.m

@@ -1,5 +1,4 @@
 #import "ARTRest+Private.h"
-
 #import "ARTChannel+Private.h"
 #import "ARTRestChannels+Private.h"
 #import "ARTDataQuery+Private.h"
@@ -335,6 +334,16 @@ - (NSString *)agentIdentifierWithWrapperSDKAgents:(nullable NSDictionary<NSStrin
     return [ARTClientInformation agentIdentifierWithAdditionalAgents:additionalAgents];
 }
 
+// Checks if the response contains any Ably header
+- (BOOL)isAblyResponse:(NSHTTPURLResponse *)response {
+    for (NSString* key in response.allHeaderFields) {
+        if ([key.lowercaseString containsString:@"-ably"]) {
+            return true;
+        }
+    }
+    return false;
+}
+
 /**
  originalRequestId is used only for fallback requests. It should never be used to execute request by yourself, it's passed from within below method.
  */
@@ -413,10 +422,14 @@ - (NSString *)agentIdentifierWithWrapperSDKAgents:(nullable NSDictionary<NSStrin
         if (response.statusCode >= 400) {
             if (data) {
                 NSError *decodeError = nil;
-                ARTErrorInfo *dataError = [self->_encoders[response.MIMEType] decodeErrorInfo:data
-                                                                                   statusCode:response.statusCode
-                                                                                        error:&decodeError];
-                if ([self shouldRenewToken:&dataError] && [request isKindOfClass:[NSMutableURLRequest class]]) {
+                ARTErrorInfo *dataError = nil;
+                id<ARTEncoder> encoder = self->_encoders[response.MIMEType];
+                
+                if (encoder && [self isAblyResponse:response]) {
+                    dataError = [encoder decodeErrorInfo:data statusCode:response.statusCode error:&decodeError];
+                }
+                
+                if (dataError && [self shouldRenewToken:&dataError] && [request isKindOfClass:[NSMutableURLRequest class]]) {
                     ARTLogDebug(self.logger, @"RS:%p retry request %@", self, request);
                     // Make a single attempt to reissue the token and resend the request
                     if (self->_tokenErrorRetries < 1) {