Use empty() instead checking size() == 0

Author: WANGJIEKE

lib/PrintAsClang/DeclAndTypePrinter.cpp

@@ -404,7 +404,7 @@ class DeclAndTypePrinter::Implementation
       }
       os << "  };\n"; // enum class cases' closing bracket
 
-      if (elementTagMapping.size() == 0) {
+      if (elementTagMapping.empty()) {
         os << "\n";
         return;
       }