MediaMetrics: Avoid creating temporary string

We change our empty string comparison, the expected common case,
to directly check the character array contents, instead of
implicitly constructing a std::string object for comparison.

Bug: 199763036
Test: TreeHugger
Change-Id: Idcb96ff6f6b86a187c4999b37670721c1adaa51d
diff --git a/media/libmediametrics/MediaMetricsItem.cpp b/media/libmediametrics/MediaMetricsItem.cpp
index 1c71f5c..a7ec975 100644
--- a/media/libmediametrics/MediaMetricsItem.cpp
+++ b/media/libmediametrics/MediaMetricsItem.cpp
@@ -70,7 +70,7 @@
 
 status_t errorStringToStatus(const char *error) {
     const auto& map = getErrorStringMap();
-    if (error == nullptr || error == "") return NO_ERROR;
+    if (error == nullptr || error[0] == '\0') return NO_ERROR;
     auto it = map.find(error);
     if (it != map.end()) {
         return it->second;