Avoid "android.media.mediacodec.log-session-id" print redundancy

set "log-session-id" media metrics only if it is not empty.

Test: adb shell dumpsys media.metrics | grep codec
Change-Id: I6c2fc61c587feb5d9dbb431aaa10157cb629866c
Signed-off-by: guochuang <guochuang@xiaomi.corp-partner.google.com>
diff --git a/media/libstagefright/MediaCodec.cpp b/media/libstagefright/MediaCodec.cpp
index 5c9f68e..e7b0c35 100644
--- a/media/libstagefright/MediaCodec.cpp
+++ b/media/libstagefright/MediaCodec.cpp
@@ -2005,7 +2005,9 @@
         mediametrics_setInt32(nextMetricsHandle, kCodecEncoder,
                               (flags & CONFIGURE_FLAG_ENCODE) ? 1 : 0);
 
-        mediametrics_setCString(nextMetricsHandle, kCodecLogSessionId, mLogSessionId.c_str());
+        if (!mLogSessionId.empty()) {
+            mediametrics_setCString(nextMetricsHandle, kCodecLogSessionId, mLogSessionId.c_str());
+        }
 
         // moved here from ::init()
         mediametrics_setCString(nextMetricsHandle, kCodecCodec, mInitName.c_str());