Fixed mistake in test_diag_int64

Author: ivan-pi

src/tests/linalg/test_linalg.f90

@@ -222,7 +222,7 @@ subroutine test_diag_int32
   end subroutine
   subroutine test_diag_int64
     integer, parameter :: n = 4
-    integer(int64) :: a(n,n), c(2*n-1)
+    integer(int64) :: a(n,n), c(0:2*n-1)
     logical :: mask(n,n)
     integer :: i, j