Clean up possible null dereference warning.

Added a runtime check for the value of the pointer.

(cherry picked from commit 88a69ded4ba00393e3865ccdfe65f964e58467b6)

Bug: b/27101951
Test: verified warnings are gone.
Merged-In: Ia1004ca6fdc0937450a72d680c02a79aab22a739
Change-Id: Ia1004ca6fdc0937450a72d680c02a79aab22a739
diff --git a/cmds/installd/CacheTracker.cpp b/cmds/installd/CacheTracker.cpp
index e293948..3eb39b9 100644
--- a/cmds/installd/CacheTracker.cpp
+++ b/cmds/installd/CacheTracker.cpp
@@ -148,6 +148,7 @@
         }
 
         // Bubble up modified time to parent
+        CHECK(p != nullptr);
         switch (p->fts_info) {
         case FTS_DP:
         case FTS_DEFAULT: