Refactor: Ensure safe error handling by removing isolated throw; statements.

- SonarCloud analysis identified standalone `throw;` calls without accompanying `try-catch` blocks, used inconsistently as placeholders or for premature termination under specific conditions.
- Removed these `throw;` instances to prevent potential runtime issues in future development phases, where such configurations might inadvertently be created.
- Introduced `assert` statements as a more appropriate mechanism for asserting preconditions in the affected class member functions, ensuring clearer intent and safer code behavior during development.
- Refactor action_kind processing to use switch() instead of if-else chains; add assertion in default case.
- Fix SonarCloud issue: Make this variable a const reference.
https://sonarcloud.io/project/issues?resolved=false&pullRequest=3104&id=owasp-modsecurity_ModSecurity&open=AY8Vpgy4f6U6E7VKL4Cn

headers/modsecurity/transaction.h

@@ -14,6 +14,7 @@
  */
 
 #ifdef __cplusplus
+#include <cassert>
 #include <ctime>
 #include <fstream>
 #include <iomanip>
@@ -307,11 +308,8 @@ class TransactionSecMarkerManagement {
     }
 
     std::shared_ptr<std::string> getCurrentMarker() const {
-        if (m_marker) {
-            return m_marker;
-        } else {
-            throw; // cppcheck-suppress rethrowNoCurrentException
-        }
+        assert((m_marker != nullptr) && "You might have forgotten to call and evaluate isInsideAMarker() before calling getCurrentMarker().");
+        return m_marker;
     }
 
     void removeMarker() {