restore these variables of not found with mkl

modules/find/FindBLAS.cmake

@@ -856,6 +856,11 @@ if( (NOT BLAS_FOUND_WITH_PKGCONFIG) OR BLAS_GIVEN_BY_USER )
         endif()
       endif (_LANGUAGES_ MATCHES C OR _LANGUAGES_ MATCHES CXX)
     endif(NOT BLAS_LIBRARIES OR BLA_VENDOR MATCHES "Intel*")
+    if (NOT BLAS_LIBRARIES)
+      set(BLAS_INCLUDE_DIRS "")
+      set(BLAS_CFLAGS_OTHER "")
+      set(BLAS_LDFLAGS_OTHER "")
+    endif()
   endif (BLA_VENDOR MATCHES "Intel*" OR BLA_VENDOR STREQUAL "All")