CSR with 0 angle bends

[iagapov]

if a bend has 0 angle in the lattice csr crashes like so

Traceback (most recent call last):
File "C:\workspace\p4-h\collective\cellA.py", line 192, in
navi.add_physics_proc(csr,lat.sequence[0], IDMARKER)
File "c:\workspace\ocelot-collab\ocelot\cpbd\optics.py", line 1067, in add_physics_proc
self.process_table.add_physics_proc(physics_proc, elem1, elem2)
File "c:\workspace\ocelot-collab\ocelot\cpbd\optics.py", line 1041, in add_physics_proc
physics_proc.prepare(self.lat)
File "c:\workspace\ocelot-collab\ocelot\cpbd\csr.py", line 627, in prepare
R = -elem.l/elem.angle
ZeroDivisionError: float division by zero

[sergey-tomin]

Fixed and committed to "dev" branch.