David Muir remains the undisputed king of the evening network news, while NBC’s Tom Llamas continues to gain ground in the demo on the perennial ratings leader. ABC’s “World News Tonight” finished June as the nation’s most-watched nightly newscast, averaging 7.82 million viewers and narrowly edging out NBC’s “Nightly News” in the advertiser-coveted 25-to-54 demographic, according to Nielsen Big Data + Panel figures. Llamas is making the race tighter in the demo. The NBC broadcast averaged 936,