title: Object reference not set to an instance of an object error show in Sitecore 7.2 updation
body: <p>When I am installing Sitecore update package 7.2 then <code>Object reference not set to an instance of an object error</code> shows up and the package is not installed:</p>
  
  <blockquote>
    <p>Server Error in '/' Application. Object reference not set to an
    instance of an object. Description: An unhandled exception occurred
    during the execution of the current web request. Please review the
    stack trace for more information about the error and where it
    originated in the code.</p>
    
    <p>Exception Details: System.NullReferenceException: Object reference not
    set to an instance of an object.</p>
    
    <p>Source Error:</p>
    
    <p>An unhandled exception was generated during the execution of the
    current web request. Information regarding the origin and location of
    the exception can be identified using the exception stack trace below.</p>
    
    <p>Stack Trace:</p>
    
    <p>[NullReferenceException: Object reference not set to an instance of an
    object.]    Sitecore.Update.InstallUpdatePackage.WriteMessage(Object
    message, Exception ex, Level level, Boolean isCommandText) +501<br>
    Sitecore.Update.InstallUpdatePackage.WriteSupportInstructions(String
    historyPath, Exception ex) +807<br>
    Sitecore.Update.InstallUpdatePackage.OnLoad(EventArgs e) +1055<br>
    System.Web.UI.Control.LoadRecursive() +70<br>
    System.Web.UI.Page.ProcessRequestMain(Boolean
    includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
    +3177</p>
  </blockquote>
  
  <p>Please go through the following details also:</p>
  
  <blockquote>
    <p>Exception details: System.Exception: Cannot execute post installation
    action because installation data not found. at
    Sitecore.Update.InstallUpdatePackage.ExecutePostStep(MetadataView
    view) at Sitecore.Update.InstallUpdatePackage.OnLoad(EventArgs e)</p>
  </blockquote>