As in water conditioner do you mean remove chorline? I usually let mine sit out for a day and the chlorine evaporates but in your case that doesn't look like it'l work how bout puting in a little water, letting some sit out overnight and tomorrow morning fill it back up, just make sure your filter tube is all the way in where it sucks up water and your heater is up to the fill line and you should be good I think.
Well, if your tank is half empty and the filter isn't running, I'd run to the store to get the conditioner (because I wouldn't pour chlorinated water in the tank). However, if there is enough water to keep the filter running, you could wait until you can go to the store to get the conditioner OR perhaps you could pour chlorinated water into some buckets and let it stand till the next day. Only remember that waiting will get rid of chlorine but not of chloramine - and a lot of municipal water supply sources use chloramine in their water, which is as dangerous to fish as chlorine.
If you call your water company and ask them if they are adding just chlorine or chlorine and chloramine (a lot of them add chloramine just in the summertime so you need to check for sure), and they tell you that they do NOT add chloramine you can boil the water and cool it and then it is safe to use as the chlorine boils out. I will warn you that you cannot cool it with ice, you have to just let it cool naturally or you will be putting chlorinated water back into it. It is also a long drawn out messy job but it works. The quick way is to put the ice water in the sink and sit the pot in the ice water but not let it get into the pot.