Quiet the CLang compiler.

(It's a false-positive, but CLang doesn't seem to know any better.)

thirdparty/nlohmann_json/nlohmann/json.hpp

@@ -6763,6 +6763,7 @@ class lexer : public lexer_base<BasicJsonType>
                                 }
                             }
                         }
+                            break;      // quiet CLang compiler
 
                         default:
                             break;