Update dielectrics.tcl

Added check of variable <<n_circles>> to ensure, that the value is not zero
If <<round($n_half_equator*sin($theta))>> in procedure "dielectric_sphere" is zero the subsequent setting of variable <<incr_phi>> leaded to a division by zero.
Merge pull request #132 from lufische/patch-1

Update dielectrics.tcl
Merge pull request #131 from ohickey/working_branch

fixed bug with reading checkpoints in the lb gpu using wrong set of node...
Fixed build error when ELECTROSTATICS is disabled.
Merge remote-tracking branch 'upstream/master' into working_branch