(plaintiff injured during horseback ride when thrown from horse and sued defendant for negligence; district court held res ipsa loquitur inapplicable and granted summary judgment for defendant because plaintiff could not establish any evidence of defendant’s negligence; plaintiff appealed; appellate court upheld finding of lack of evidence of negligence and lack of evidence in records of disputed issues; appellate court dismissed theory of negligence first presented on appeal that plaintiff should not have been allowed to ride in front of trail guide; denial of res ipsa loquitur theory also affirmed because riding a horse is inherently dangerous despite precautionary efforts to avoid accidents).