Migrate from android::String isEmpty to empty

This empty method is different from the old one - it aligns with
std::string definition.

Bug: 295394788
Test: make checkbuild
Change-Id: Id74502de0e51182aa9629db8dc70739be4483d12
diff --git a/services/sensorservice/SensorService.cpp b/services/sensorservice/SensorService.cpp
index 1030cee..c69b072 100644
--- a/services/sensorservice/SensorService.cpp
+++ b/services/sensorservice/SensorService.cpp
@@ -609,7 +609,7 @@
             for (auto&& i : mRecentEvent) {
                 std::shared_ptr<SensorInterface> s = getSensorInterfaceFromHandle(i.first);
                 if (!i.second->isEmpty() && s != nullptr) {
-                    if (privileged || s->getSensor().getRequiredPermission().isEmpty()) {
+                    if (privileged || s->getSensor().getRequiredPermission().empty()) {
                         i.second->setFormat("normal");
                     } else {
                         i.second->setFormat("mask_data");
@@ -735,7 +735,7 @@
     for (auto&& i : mRecentEvent) {
         std::shared_ptr<SensorInterface> s = getSensorInterfaceFromHandle(i.first);
         if (!i.second->isEmpty() && s != nullptr) {
-            i.second->setFormat(privileged || s->getSensor().getRequiredPermission().isEmpty() ?
+            i.second->setFormat(privileged || s->getSensor().getRequiredPermission().empty() ?
                     "normal" : "mask_data");
             const uint64_t mToken = proto.start(service::SensorEventsProto::RECENT_EVENTS_LOGS);
             proto.write(service::SensorEventsProto::RecentEventsLog::NAME,