fix srpm builds after fe065f8

Author: vuvova

cmake/Internal/CPack/CPackRPM.cmake

@@ -18,7 +18,8 @@ macro(restore WHAT)
 endmacro()
 
 foreach (WHAT SUMMARY DESCRIPTION)
-  if(NOT CPACK_RPM_${CPACK_RPM_PACKAGE_COMPONENT}_PACKAGE_${WHAT})
+  if(CPACK_RPM_PACKAGE_COMPONENT AND
+     NOT CPACK_RPM_${CPACK_RPM_PACKAGE_COMPONENT}_PACKAGE_${WHAT})
     message(FATAL_ERROR "CPACK_RPM_${CPACK_RPM_PACKAGE_COMPONENT}_PACKAGE_${WHAT} is not defined")
   endif()
 endforeach()