Skin for * cannot be found

Problem:

Error: Skin for riageekapp0 cannot be found.
    at spark.components.supportClasses::SkinnableComponent/loadSkin()[E:\dev\i11.5\frameworks\projects\flex4\src\spark\components\supportClasses\SkinnableComponent.as:460]
    at spark.components.supportClasses::SkinnableComponent/validateSkinChange()[E:\dev\i11.5\frameworks\projects\flex4\src\spark\components\supportClasses\SkinnableComponent.as:240]
    at spark.components.supportClasses::SkinnableComponent/createChildren()[E:\dev\i11.5\frameworks\projects\flex4\src\spark\components\supportClasses\SkinnableComponent.as:210]
    at spark.components::SkinnableContainer/createChildren()[E:\dev\i11.5\frameworks\projects\flex4\src\spark\components\SkinnableContainer.as:797]
    at mx.core::UIComponent/initialize()[E:\dev\i11.5\frameworks\projects\framework\src\mx\core\UIComponent.as:6632]
    at spark.components::Application/initialize()[E:\dev\i11.5\frameworks\projects\flex4\src\spark\components\Application.as:678]
    at thingsapp/initialize()
    at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::childAdded()[E:\dev\i11.5\frameworks\projects\framework\src\mx\managers\SystemManager.as:2214]
    at mx.managers::SystemManager/initializeTopLevelWindow()[E:\dev\i11.5\frameworks\projects\framework\src\mx\managers\SystemManager.as:3558]
    at mx.managers::SystemManager/http://www.adobe.com/2006/flex/mx/internal::docFrameHandler()[E:\dev\i11.5\frameworks\projects\framework\src\mx\managers\SystemManager.as:3343]
    at mx.managers::SystemManager/docFrameListener()[E:\dev\i11.5\frameworks\projects\framework\src\mx\managers\SystemManager.as:3201]

Solution: I was using different build of Gumbo, so the library(swc) created in one version was not able to found some classes. To fix this error, make sure that you are using same version of build for both your library(swc) and the application project.