Translate a 'paged' string to int if passed to Query_Args

If we use Query_Args::merge_query and the current URL is /page/<number> the
"paged" value is passed as a string and causes a fatal error.

dev/wp-unit/tests/Query/ArgsTest.php

@@ -48,4 +48,14 @@ public function test_merge_query(): void {
 		$this->assertEquals( $previous, $query->query_vars );
 	}
 
+
+	public function test_string_paged(): void {
+		$query = new \WP_Query();
+		$query->parse_query( [
+			'paged' => '2',
+		] );
+		$args = new Query_Args( [] );
+		$args->merge_query( $query );
+		$this->assertEquals( 2, $args->get_args()['paged'] );
+	}
 }

src/Query/Query_Args.php

@@ -633,7 +633,11 @@ public function orderby( array|string $orderby, string $order = '' ): void {
 	public function merge_query( \WP_Query $query ): void {
 		foreach ( $query->query as $arg => $value ) {
 			if ( '' !== $value && \property_exists( $this, $arg ) && ! isset( $this->{$arg} ) ) {
-				$this->{$arg} = $value;
+				if ( 'paged' === $arg ) {
+					$this->{$arg} = (int) $value;
+				} else {
+					$this->{$arg} = $value;
+				}
 			}
 		}
 		$local_args = $this->get_args();