Always set $handles to false when empty

When invoked as a hooked callback, it receives an empty string.
Empty is the same as false.

lib/experimental/fonts-api/fonts-api.php

@@ -198,21 +198,17 @@ function wp_print_fonts( $handles = false ) {
 			return array();
 		}
 
-		if ( false === $handles ) {
+		if ( empty( $handles ) ) {
 			// Automatically enqueue all user-selected fonts.
 			WP_Fonts_Resolver::enqueue_user_selected_fonts();
-		} else {
-			// When `true`, print all registered fonts for the iframed editor.
-			if ( $in_iframed_editor ) {
-				$queue           = $wp_fonts->queue;
-				$done            = $wp_fonts->done;
-				$wp_fonts->done  = array();
-				$wp_fonts->queue = $registered;
-				$handles         = false;
-			} elseif ( empty( $handles ) ) {
-				// When falsey, assign `false` to print enqueued fonts.
-				$handles = false;
-			}
+			$handles = false;
+		} elseif ( $in_iframed_editor ) {
+			// Print all registered fonts for the iframed editor.
+			$queue           = $wp_fonts->queue;
+			$done            = $wp_fonts->done;
+			$wp_fonts->done  = array();
+			$wp_fonts->queue = $registered;
+			$handles         = false;
 		}
 
 		_wp_scripts_maybe_doing_it_wrong( __FUNCTION__ );