Fix migrate authors query pagination

Author: mattheu

inc/cli/class-migrate-command.php

@@ -128,7 +128,11 @@ public function wp_authors( $args, $assoc_args ) : void {
 			WP_CLI::line( sprintf( 'Processed %d posts, pausing for a breath...', $count ) );
 			sleep( 2 );
 
-			$paged++;
+			// When not overwriting, or during a dry run,
+			// need to skip pagination due to NOT EXISTS tax query.
+			if ( $dry_run || $overwrite ) {
+				$paged++;
+			}
 		} while ( count( $posts ) );
 
 		if ( true === $dry_run ) {