fix check multipart data

src/main/kotlin/co/id/datacomsolusindo/ipphonebridge/BridgeFIlter.kt

@@ -81,7 +81,8 @@ class BridgeFilter(private val template: SimpMessagingTemplate, val resourceLoad
                     val rb = RequestBuilder(reqId, toPath, HttpMethod.valueOf(req.method), headerMap.toMutableMap())
 
                     rb.queryString = req.queryString
-                    if (req.contentType != null && req.contentType.toLowerCase().contains("multipart/form-data")) {
+
+                    if (req.contentType?.toLowerCase()?.contains("multipart/form-data") == true) {
                         rb.parts =
                             req.parts.map {
                                 val subFilename = if (it.submittedFileName == null) {