smtp/files: don't modify prev file on open failure

src/app-layer-smtp.c

@@ -529,8 +529,9 @@ int SMTPProcessDataChunk(const uint8_t *chunk, uint32_t len,
                         (uint8_t *)entity->filename, flen, (uint8_t *)chunk, len, flags) != 0) {
                 ret = MIME_DEC_ERR_DATA;
                 SCLogDebug("FileOpenFile() failed");
-            }
+            } else {
                 SMTPNewFile(tx, files->tail);
+            }
 
             /* If close in the same chunk, then pass in empty bytes */
             if (state->body_end) {