Question: Maple code error

Hi, i have problem with this code: 

Spacer := proc (N, p, q, sa, sb, M) local A, B, r, PA, PC, PB, stan, krok, droga; A := -N; B := N; r := 1-p-q; PA := empirical[0., sa, 1-sa]; PC := empirical[q, r, p]; PB := empirical[1-sb, sb, 0.]; stan := 0; droga := stan; to M do if A < stan and stan < B then krok := random[PC](1)-2 elif stan = A then krok := random[PA](1)-2 elif stan = B then krok := random[PB](1)-2 end if; stan := stan+krok; droga := droga, stan end do; {}*plots[pointplot]([seq([i, droga[i+1]], i = 0 .. nops([droga])-1)], axes = BOXED) end proc

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i have error when i start procedure like: 

error, (in Spacer) cannot determine if this expression is true or false: 0 < random[empirical[.5, 0.5e-1, .45]](1)+8 and random[empirical[.5, 0.5e-1, .45]](1) < 12

My run command: Spacer(3,0.5,0.5,0.8,0.8,20);

Please help me.