fix: Setting DDPR Consents on iOS (#23)

Author: BrandonStalnaker

plugin/src/ios/CDVMParticle.m

@@ -72,7 +72,7 @@ - (void)setATTStatus:(CDVInvokedUrlCommand*)command {
 - (void)addGDPRConsentState:(CDVInvokedUrlCommand*)command {
     [self.commandDelegate runInBackground:^{
         NSMutableDictionary *serializedConsent = [command.arguments objectAtIndex:0];
-        NSString *purpose = [command.arguments objectAtIndex:0];
+        NSString *purpose = [command.arguments objectAtIndex:1];
 
         MPGDPRConsent *consent = [CDVMParticle MPGDPRConsent:serializedConsent];
         MPConsentState *consentState = [[MParticle sharedInstance].identity.currentUser.consentState copy];