[igraph] errors using power.law.fit

[Martin Tomko]

Dear all,
I am running a batch process on a few hundreds graphs, and trying to get 
their power.law.fit exponents. Every now and then I get an error:

Error in optim(start, f, method = method, hessian = TRUE, ...) :
  non-finite finite-difference value [1]


Which I assume arises from the use of power.law.fit - google seems to 
imply that optim() is related to statistical fitting. Now, it is 
possible that some of the graphs I have would not fit a power law well - 
is there a recommended way for checking whether it makes sense at all to 
try fitting one?

Thanks,
Martin