FS-4860 --resolve This seems to have come from a malformed file_string in the ringback var

src/mod/applications/mod_dptools/mod_dptools.c

@@ -4476,8 +4476,13 @@ static switch_status_t next_file(switch_file_handle_t *handle)
 		} else {
 			switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "Error finding the folder path section in '%s'\n", path);
 		}
-
 	}
+
+	if (switch_file_exists(file, handle->memory_pool) != SWITCH_STATUS_SUCCESS) {
+		switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_ERROR, "File [%s] does not exist.\n", file);
+		goto top;
+	}
+
 	if (switch_core_file_open(&context->fh, file, handle->channels, handle->samplerate, handle->flags, NULL) != SWITCH_STATUS_SUCCESS) {
 		goto top;
 	}