Fixed wrong inverted condition

src/bootstrap-table.js

@@ -1958,7 +1958,7 @@ class BootstrapTable {
     if (
       this.options.search &&
       this.options.sidePagination === 'server' &&
-      this.columns.filter(column => !column.searchable).length
+      this.columns.filter(column => column.searchable).length
     ) {
       params.searchable = []