Bug 971975 - Proper state and non-null check for CacheFile::WriteMetadataIfNeededLocked(), r=michal

netwerk/cache2/CacheFile.cpp

@@ -177,8 +177,10 @@ CacheFile::~CacheFile()
   LOG(("CacheFile::~CacheFile() [this=%p]", this));
 
   MutexAutoLock lock(mLock);
-  if (!mMemoryOnly)
+  if (!mMemoryOnly && mReady) {
+    // mReady flag indicates we have metadata plus in a valid state.
     WriteMetadataIfNeededLocked(true);
+  }
 }
 
 nsresult
@@ -1335,6 +1337,11 @@ CacheFile::WriteMetadataIfNeededLocked(bool aFireAndForget)
   AssertOwnsLock();
   MOZ_ASSERT(!mMemoryOnly);
 
+  if (!mMetadata) {
+    MOZ_CRASH("Must have metadata here");
+    return;
+  }
+
   if (!aFireAndForget) {
     // if aFireAndForget is set, we are called from dtor. Write
     // scheduler hard-refers CacheFile otherwise, so we cannot be here.