[core] Tweak conversions to reduce binary size

* return {} → return nullopt
* error = { "..." } → error.message = "..."

1 files changed, 6 insertions, 6 deletions

diff --git a/src/mbgl/style/conversion/transition_options.cpp b/src/mbgl/style/conversion/transition_options.cpp
index 116d44f9d9..924032a0c0 100644
--- a/src/mbgl/style/conversion/transition_options.cpp
+++ b/src/mbgl/style/conversion/transition_options.cpp
@@ -6,8 +6,8 @@ namespace conversion {
 
 optional<TransitionOptions> Converter<TransitionOptions>::operator()(const Convertible& value, Error& error) const {
     if (!isObject(value)) {
-        error = { "transition must be an object" };
-        return {};
+        error.message = "transition must be an object";
+        return nullopt;
     }
 
     optional<TransitionOptions> result = TransitionOptions{};
@@ -16,8 +16,8 @@ optional<TransitionOptions> Converter<TransitionOptions>::operator()(const Conve
     if (duration) {
         auto number = toNumber(*duration);
         if (!number) {
-            error = { "duration must be a number" };
-            return {};
+            error.message = "duration must be a number";
+            return nullopt;
         }
         result->duration = { std::chrono::milliseconds(int64_t(*number)) };
     }
@@ -26,8 +26,8 @@ optional<TransitionOptions> Converter<TransitionOptions>::operator()(const Conve
     if (delay) {
         auto number = toNumber(*delay);
         if (!number) {
-            error = { "delay must be a number" };
-            return {};
+            error.message = "delay must be a number";
+            return nullopt;
         }
         result->delay = { std::chrono::milliseconds(int64_t(*number)) };
     }