✅ add tests to improve coverage

include/nlohmann/detail/input/binary_reader.hpp

@@ -1577,8 +1577,8 @@ class binary_reader
                 return get_number(input_format_t::msgpack, result.subtype) and get_binary(input_format_t::msgpack, 16, result);
             }
 
-            default:            // LCOV_EXCL_LINE
-                assert(false);  // LCOV_EXCL_LINE
+            default:           // LCOV_EXCL_LINE
+                return false;  // LCOV_EXCL_LINE
         }
     }