add MisbehavedSSCSMException type

src/exceptions.h

@@ -87,6 +87,11 @@ public:
 	ModError(const std::string &s): BaseException(s) {}
 };
 
+class MisbehavedSSCSMException : public BaseException {
+public:
+	MisbehavedSSCSMException(const std::string &s): BaseException(s) {}
+};
+
 
 /*
 	Some "old-style" interrupts:

src/script/sscsm/sscsm_requests.h

@@ -74,7 +74,7 @@ struct SSCSMRequestLog : public ISSCSMRequest
 	SerializedSSCSMAnswer exec(Client *client) override
 	{
 		if (level >= LL_MAX) {
-			throw BaseException("Tried to log at non-existent level."); // TODO: choose better exception type
+			throw MisbehavedSSCSMException("Tried to log at non-existent level.");
 		} else {
 			g_logger.log(level, text);
 		}