[observer] Don't crash if port info can not be fetched
[observer] Don't crash if port info can not be fetched

When the observed node is older than OTP-19.0,
observer_backend:get_port_list/1 does not exist. Observer would
earliger crash in this situation. This is now corrected and a popup
is displayed instead.

vinoski/otp,isvilen/otp,bjorng/otp,RoadRunnr/otp,rlipscombe/otp,fenollp/otp,mikpe/otp,electricimp/otp,fenollp/otp,vinoski/otp,potatosalad/otp,g-andrade/otp,isvilen/otp,jj1bdx/otp,electricimp/otp,bsmr-erlang/otp,matwey/otp,matwey/otp,erlang/otp,RaimoNiskanen/otp,tuncer/otp,tuncer/otp,bjorng/otp,goertzenator/otp,bernardd/otp,ferd/otp,bsmr-erlang/otp,electricimp/otp,rlipscombe/otp,matwey/otp,fenollp/otp,uabboli/otp,electricimp/otp,saleyn/otp,electricimp/otp,vinoski/otp,RoadRunnr/otp,jj1bdx/otp,bernardd/otp,vladdu/otp,bernardd/otp,bjorng/otp,ferd/otp,lrascao/otp,dumbbell/otp,getong/otp,jj1bdx/otp,ferd/otp,aboroska/otp,RaimoNiskanen/otp,saleyn/otp,RoadRunnr/otp,vladdu/otp,falkevik/otp,kvakvs/otp,goertzenator/otp,mikpe/otp,lrascao/otp,mikpe/otp,potatosalad/otp,rlipscombe/otp,kvakvs/otp,emacsmirror/erlang,dgud/otp,isvilen/otp,RoadRunnr/otp,dgud/otp,falkevik/otp,erlang/otp,falkevik/otp,erlang/otp,lrascao/otp,tuncer/otp,g-andrade/otp,jj1bdx/otp,RoadRunnr/otp,bernardd/otp,falkevik/otp,bjorng/otp,ferd/otp,aboroska/otp,potatosalad/otp,erlang/otp,tuncer/otp,dgud/otp,vinoski/otp,electricimp/otp,goertzenator/otp,vladdu/otp,matwey/otp,dgud/otp,rlipscombe/otp,electricimp/otp,bsmr-erlang/otp,isvilen/otp,bernardd/otp,g-andrade/otp,uabboli/otp,fenollp/otp,kvakvs/otp,jj1bdx/otp,aboroska/otp,vinoski/otp,bjorng/otp,bjorng/otp,bernardd/otp,legoscia/otp,fenollp/otp,tuncer/otp,dgud/otp,lrascao/otp,rlipscombe/otp,aboroska/otp,bjorng/otp,bernardd/otp,uabboli/otp,saleyn/otp,mikpe/otp,getong/otp,getong/otp,falkevik/otp,legoscia/otp,g-andrade/otp,getong/otp,g-andrade/otp,RaimoNiskanen/otp,lrascao/otp,saleyn/otp,kvakvs/otp,bsmr-erlang/otp,erlang/otp,emacsmirror/erlang,RaimoNiskanen/otp,ferd/otp,falkevik/otp,jj1bdx/otp,goertzenator/otp,tuncer/otp,lrascao/otp,tuncer/otp,kvakvs/otp,tuncer/otp,vladdu/otp,jj1bdx/otp,emacsmirror/erlang,RaimoNiskanen/otp,g-andrade/otp,getong/otp,RaimoNiskanen/otp,goertzenator/otp,aboroska/otp,erlang/otp,dgud/otp,dumbbell/otp,dumbbell/otp,vladdu/otp,bjorng/otp,g-andrade/otp,lrascao/otp,emacsmirror/erlang,matwey/otp,cobusc/otp,mikpe/otp,jj1bdx/otp,dumbbell/otp,vinoski/otp,cobusc/otp,dgud/otp,legoscia/otp,vinoski/otp,fenollp/otp,goertzenator/otp,RoadRunnr/otp,bsmr-erlang/otp,bsmr-erlang/otp,dgud/otp,rlipscombe/otp,emacsmirror/erlang,emacsmirror/erlang,dumbbell/otp,uabboli/otp,uabboli/otp,vladdu/otp,uabboli/otp,bsmr-erlang/otp,isvilen/otp,potatosalad/otp,cobusc/otp,dumbbell/otp,erlang/otp,cobusc/otp,vinoski/otp,matwey/otp,RaimoNiskanen/otp,uabboli/otp,bsmr-erlang/otp,cobusc/otp,dumbbell/otp,RaimoNiskanen/otp,dumbbell/otp,rlipscombe/otp,saleyn/otp,isvilen/otp,erlang/otp,emacsmirror/erlang,electricimp/otp,ferd/otp,vinoski/otp,vinoski/otp,potatosalad/otp,falkevik/otp,emacsmirror/erlang,kvakvs/otp,bsmr-erlang/otp,legoscia/otp,rlipscombe/otp,lrascao/otp,legoscia/otp,uabboli/otp,rlipscombe/otp,vladdu/otp,electricimp/otp,saleyn/otp,RaimoNiskanen/otp,potatosalad/otp,matwey/otp,erlang/otp,vladdu/otp,aboroska/otp,ferd/otp,potatosalad/otp,g-andrade/otp,potatosalad/otp,emacsmirror/erlang,goertzenator/otp,isvilen/otp,fenollp/otp,potatosalad/otp,isvilen/otp,mikpe/otp,falkevik/otp,legoscia/otp,cobusc/otp,matwey/otp,kvakvs/otp,bernardd/otp,jj1bdx/otp,RoadRunnr/otp,dumbbell/otp,emacsmirror/erlang,mikpe/otp,aboroska/otp,getong/otp,goertzenator/otp,legoscia/otp,legoscia/otp,aboroska/otp,ferd/otp,tuncer/otp,cobusc/otp,mikpe/otp,dgud/otp,jj1bdx/otp,saleyn/otp,uabboli/otp,aboroska/otp,saleyn/otp,cobusc/otp,mikpe/otp,rlipscombe/otp,vladdu/otp,kvakvs/otp,g-andrade/otp,RoadRunnr/otp,isvilen/otp,lrascao/otp,dgud/otp,falkevik/otp,kvakvs/otp,fenollp/otp,mikpe/otp,getong/otp,bjorng/otp,fenollp/otp,erlang/otp,dumbbell/otp,bjorng/otp,ferd/otp,saleyn/otp,RoadRunnr/otp,goertzenator/otp,getong/otp,matwey/otp,getong/otp,isvilen/otp,getong/otp,potatosalad/otp,bernardd/otp,legoscia/otp,g-andrade/otp