Fix exception when parsing invalid version

lib/structs/responses/version.cpp

@@ -4,8 +4,6 @@
 
 #include <nlohmann/json.hpp>
 
-const static std::regex VERSION_REGEX("r(\\d+)\\.(\\d+)\\.(\\d+)");
-
 namespace mtx {
 namespace responses {
 
@@ -15,7 +13,7 @@ from_json(const nlohmann::json &obj, Versions &response)
     response.versions = obj.at("versions").get<std::vector<std::string>>();
 
     for (auto &version : response.versions) {
-        if (!std::regex_match(version, VERSION_REGEX))
+        if (version.empty())
             throw std::invalid_argument(version + ": invalid version");
     }
 }

tests/responses.cpp

@@ -484,7 +484,7 @@ TEST(Responses, Versions)
 
     json error_data = R"({
 	  "versions" : [
-	    "r.0.0.1"
+	    ""
 	  ]
         })"_json;