[core] Convert null to empty string, not “null”

1 files changed, 1 insertions, 0 deletions

diff --git a/src/mbgl/style/expression/compound_expression.cpp b/src/mbgl/style/expression/compound_expression.cpp
index 3bd8a836df..4739d50168 100644
--- a/src/mbgl/style/expression/compound_expression.cpp
+++ b/src/mbgl/style/expression/compound_expression.cpp
@@ -303,6 +303,7 @@ std::unordered_map<std::string, CompoundExpressionRegistry::Definition> initiali
 
     define("to-string", [](const Value& value) -> Result<std::string> {
         return value.match(
+            [](const NullValue&) -> Result<std::string> { return std::string(); },
             [](const Color& c) -> Result<std::string> { return c.stringify(); }, // avoid quoting
             [](const std::string& s) -> Result<std::string> { return s; }, // avoid quoting
             [](const auto& v) -> Result<std::string> { return stringify(v); }