logd: LogStatistics leak

- uid = -1 in subtract operation to match add

Change-Id: I7d0b85b5334c5264fd04309cb78e0c9aec0ad261
diff --git a/logd/LogStatistics.cpp b/logd/LogStatistics.cpp
index 1305b0a..6f3a088 100644
--- a/logd/LogStatistics.cpp
+++ b/logd/LogStatistics.cpp
@@ -307,6 +307,10 @@
 }
 
 void LidStatistics::subtract(unsigned short size, uid_t uid, pid_t pid) {
+    if (uid == (uid_t) -1) { // init
+        uid = (uid_t) AID_ROOT;
+    }
+
     UidStatisticsCollection::iterator it;
     for (it = begin(); it != end(); ++it) {
         UidStatistics *u = *it;