Account for non-string values sent to json_to_datetime

Author: jtsternberg

includes/CMB2_Utils.php

@@ -583,6 +583,10 @@ public static function unserialize_datetime( $date_value ) {
 	 * @return DateTime|null
 	 */
 	public static function json_to_datetime( $json_string ) {
+		if ( ! is_string( $json_string ) ) {
+			return null;
+		}
+
 		$json = json_decode( $json_string );
 
 		// Check if json decode was successful

tests/test-cmb-utils.php

@@ -370,6 +370,7 @@ public function test_json_to_datetime() {
 
 		$this->assertEquals( $datetime, CMB2_Utils::json_to_datetime( $json ) );
 		$this->assertNull( CMB2_Utils::json_to_datetime( $evil_eval ) );
+		$this->assertNull( CMB2_Utils::json_to_datetime( [ $json ] ) );
 	}
 
 }