Resolves an issue where writetofile fails when NULL is included in Nsarray and Nsdictionary

 solve the problem of  writetofile failure when NULL is included in Nsarray and Nsdictionary 

@implementation Nsarray (Plist)-(BOOL) Writetoplistfile: (nsstring*) filename{nsdata * data = [Nskeyedarchiver archived
    Datawithrootobject:self];
    Nsarray * paths = Nssearchpathfordirectoriesindomains (NSDocumentDirectory, Nsuserdomainmask, YES);
    NSString * documentsdirectory = [paths objectatindex:0];
    NSString * Path = [Documentsdirectory stringbyappendingpathcomponent:filename];
    BOOL didwritesuccessfull = [data Writetofile:path atomically:yes];
return didwritesuccessfull; } + (nsarray*) Readfromplistfile: (nsstring*) filename{nsarray * paths = Nssearchpathfordirectoriesindomains (NSDocument
    Directory, Nsuserdomainmask, YES);
    NSString * documentsdirectory = [paths objectatindex:0];
    NSString * Path = [Documentsdirectory stringbyappendingpathcomponent:filename];
    NSData * data = [NSData Datawithcontentsoffile:path];
return [Nskeyedunarchiver Unarchiveobjectwithdata:data]; } @end//needs to is set for implementation