Correct format string for optional parameters

Fixes #34
If the request already contains optional parameters, the format string is slightly different for GET
requests as the access_token is no longer the only parameter.

classes/PhFacebook.m

@@ -181,9 +181,18 @@ - (void) sendFacebookRequest: (NSDictionary*) allParams
         BOOL postRequest = [[allParams objectForKey: @"postRequest"] boolValue];
 
         if (postRequest)
+        {
             str = [NSString stringWithFormat: kFBGraphApiPostURL, request];
+        }
         else
-            str = [NSString stringWithFormat: kFBGraphApiGetURL, request, _authToken.authenticationToken];
+        {
+            // Check if request already has optional parameters
+            NSString *formatStr = kFBGraphApiGetURL;
+            NSRange rng = [request rangeOfString:@"?"];
+            if (rng.length > 0)
+                formatStr = kFBGraphApiGetURLWithParams;
+            str = [NSString stringWithFormat: formatStr, request, _authToken.authenticationToken];
+        }
 
 
         NSDictionary *params = [allParams objectForKey: @"params"];

private/PhFacebook_URLs.h

@@ -22,6 +22,7 @@
 #define kFBErrorReason @"error_description="
 
 #define kFBGraphApiGetURL @"https://graph.facebook.com/%@?access_token=%@"
+#define kFBGraphApiGetURLWithParams @"https://graph.facebook.com/%@&access_token=%@"
 
 #define kFBGraphApiPostURL @"https://graph.facebook.com/%@"