A business facing negligence claims over flash bangs used in an emergency vehicle show cannot look to its insurer for help, a federal judge held.In a written opinion Monday, U.S. District Judge Virginia M. Kendall of the Northern District of Illinois granted summary judgment in favor of The Cincinnati Specialty Underwriters Insurance Co. in a lawsuit it filed against Chicagoland Emergency Vehicle Show LLC.Cincinnati Specialty Underwriters sought a declaratory judgment that a commercial general liability policy it issued to …