@omz

Bug report

```
from sympy import re, im, E, I
from sympy import *
import numpy as np
x,y,z = symbols('x y z')
mat = Matrix([
[exp(I*x)*exp(I*z)* (1+cos(y))/2,
exp(I*z)*(-1/sqrt(2))*sin(y),
exp(-I*x)*exp(I*z)* (1-cos(y))/2],
[exp(I*x)*(1/sqrt(2))*sin(y),
cos(y),
exp(-I*x)*(-1/sqrt(2))*sin(y)],
[exp(I*x)*exp(-I*z)* (1-cos(y))/2,
exp(-I*z)*(1/sqrt(2))*sin(y),
exp(-I*x)*exp(-I*z)*(1+cos(y))/2]
])
vec = Matrix([1,0,0])
x1,y1,z1 = symbols('x1 y1 z1')
mat1 = Subs(mat,(x,y,z),(x1,y1,z1))
vec1 = Matrix([1,0,0])
a,b = symbols('a b')
PSI = cos(a/2)*(mat*vec) + sin(a/2)*exp(I*b)*(mat1*vec1) # XXX
pprint(mat1.doit()*vec)
```

If I put ".doit()" after mat1 in the line commented by XXX

The app crashes

I dont know why ... :-(

Hope you can solve it, it is quite annoying

But in general I love Pythonista :-D