don't print style message if --enable=style is not specified.

message was of type:
(style) Redundant checking of STL container element existence before removing it.

lib/checkstl.cpp

@@ -918,6 +918,9 @@ void CheckStl::sizeError(const Token *tok)
 
 void CheckStl::redundantCondition()
 {
+    if (!_settings->isEnabled("style"))
+        return;
+
     const SymbolDatabase *symbolDatabase = _tokenizer->getSymbolDatabase();
 
     for (std::list<Scope>::const_iterator i = symbolDatabase->scopeList.begin(); i != symbolDatabase->scopeList.end(); ++i) {