Initialize list_channels_with_filter result vec with capacity

Author: ViktorTigerstrom

lightning/src/ln/channelmanager.rs

@@ -1581,14 +1581,13 @@ where
 	}
 
 	fn list_channels_with_filter<Fn: FnMut(&(&[u8; 32], &Channel<<SP::Target as SignerProvider>::Signer>)) -> bool + Copy>(&self, f: Fn) -> Vec<ChannelDetails> {
-		let mut res = Vec::new();
 		// Allocate our best estimate of the number of channels we have in the `res`
 		// Vec. Sadly the `short_to_chan_info` map doesn't cover channels without
 		// a scid or a scid alias, and the `id_to_peer` shouldn't be used outside
 		// of the ChannelMonitor handling. Therefore reallocations may still occur, but is
 		// unlikely as the `short_to_chan_info` map often contains 2 entries for
 		// the same channel.
-		res.reserve(self.short_to_chan_info.read().unwrap().len());
+		let mut res = Vec::with_capacity(self.short_to_chan_info.read().unwrap().len());
 		{
 			let best_block_height = self.best_block.read().unwrap().height();
 			let per_peer_state = self.per_peer_state.read().unwrap();