FIX: Transaction::GetResultSet() now always returns a good reference

Summary

See title. For #11 (closed).

Focus

Is the unique_ptr handling correct?

Test Environment

Just run the unit tests. They failed before the fix.

Check List for the Author

• All automated tests pass
• Reference related Issues
• Up-to-date CHANGELOG.md
• Annotations in code (Gitlab comments)
  • Intent of new code
  • Problems with old code
  • Why this implementation?

Check List for the Reviewer

• I understand the intent of this MR
• All automated tests pass
• Up-to-date CHANGELOG.md
• The test environment setup works and the intended behavior is reproducible in the test environment
• In-code documentation and comments are up-to-date.
• Check: Are there specifications? Are they satisfied?

For further good practices have a look at our review guidelines.

include/caosdb/utility.h

@@ -97,7 +97,7 @@ inline auto load_string_file(const path &path) -> std::string {
 /**
  * @brief Return the environment variable KEY, or FALLBACK if it does not exist.
  */
-inline auto get_env_var(const char *key, const char *fallback) -> const char * {
+inline auto get_env_fallback(const char *key, const char *fallback) -> const char * {
   const char *val = getenv(key);
   if (val == nullptr) {
     return fallback;
@@ -110,8 +110,8 @@ inline auto get_env_var(const char *key, const char *fallback) -> const char * {
  * @brief Return the value of an environment variable or - if undefined - the
  * fallback value.
  */
-inline auto get_env_var(const std::string &key, const std::string &fallback) -> const std::string {
-  const char *val = get_env_var(key.c_str(), fallback.c_str());
+inline auto get_env_fallback(const std::string &key, const std::string &fallback) -> const std::string {
+  const char *val = get_env_fallback(key.c_str(), fallback.c_str());
 
   auto const result = std::string(val);
   return result;