Fix MSVC warning C4804

Full message of the warning:
webui\api\searchcontroller.cpp(54): warning C4804: '>': unsafe use of type 'bool'
in operation

src/webui/api/searchcontroller.cpp

@@ -51,7 +51,7 @@ namespace
     void removeActiveSearch(ISession *session, const int id)
     {
         auto activeSearches = session->getData<QSet<int>>(ACTIVE_SEARCHES);
-        if (activeSearches.remove(id) > 0)
+        if (activeSearches.remove(id))
             session->setData(ACTIVE_SEARCHES, QVariant::fromValue(activeSearches));
     }
 }