message: In CMakeLists.txt, fix MFEM_TPL_INCLUDE_DIRS when no TPLs are used.
diff: @@ -425,6 +425,9 @@ export(PACKAGE ${PROJECT_NAME})
  # Extract the include directories required to use MFEM
  get_target_property(MFEM_TPL_INCLUDE_DIRS mfem INCLUDE_DIRECTORIES)
  +if (NOT MFEM_TPL_INCLUDE_DIRS)
  + set(MFEM_TPL_INCLUDE_DIRS "")
  +endif()
  # This is the build-tree version
  set(INCLUDE_INSTALL_DIRS ${PROJECT_BINARY_DIR} ${MFEM_TPL_INCLUDE_DIRS})
  