-list (REMOVE_DUPLICATES 3RDPARTY_INCLUDE_DIRS)
-string (REGEX REPLACE ";" "\n\t" 3RDPARTY_INCLUDE_DIRS_WITH_ENDS "${3RDPARTY_INCLUDE_DIRS}")
-message (STATUS "The directories containing 3rdparty headers: ${3RDPARTY_INCLUDE_DIRS_WITH_ENDS}")
-include_directories (${3RDPARTY_INCLUDE_DIRS})
-
-list (REMOVE_DUPLICATES 3RDPARTY_LIBRARY_DIRS)
-string (REGEX REPLACE ";" "\n\t" 3RDPARTY_LIBRARY_DIRS_WITH_ENDS "${3RDPARTY_LIBRARY_DIRS}")
-message (STATUS "The directories containing 3rdparty libraries: ${3RDPARTY_LIBRARY_DIRS_WITH_ENDS}")
-link_directories (${3RDPARTY_LIBRARY_DIRS})
+if (3RDPARTY_INCLUDE_DIRS)
+ list (REMOVE_DUPLICATES 3RDPARTY_INCLUDE_DIRS)
+ string (REGEX REPLACE ";" "\n\t" 3RDPARTY_INCLUDE_DIRS_WITH_ENDS "${3RDPARTY_INCLUDE_DIRS}")
+ message (STATUS "The directories containing 3rdparty headers: ${3RDPARTY_INCLUDE_DIRS_WITH_ENDS}")
+ include_directories (${3RDPARTY_INCLUDE_DIRS})
+endif()
+
+if (3RDPARTY_LIBRARY_DIRS)
+ list (REMOVE_DUPLICATES 3RDPARTY_LIBRARY_DIRS)
+ string (REGEX REPLACE ";" "\n\t" 3RDPARTY_LIBRARY_DIRS_WITH_ENDS "${3RDPARTY_LIBRARY_DIRS}")
+ message (STATUS "The directories containing 3rdparty libraries: ${3RDPARTY_LIBRARY_DIRS_WITH_ENDS}")
+ link_directories (${3RDPARTY_LIBRARY_DIRS})
+endif()