Fixed an off-by-one error in the dtor.

rdf/base/src/nsInMemoryDataSource.cpp

@@ -824,7 +824,7 @@ InMemoryDataSource::~InMemoryDataSource(void)
         mReverseArcs = nsnull;
     }
     if (mObservers) {
-        for (PRInt32 i = mObservers->Count(); i >= 0; --i) {
+        for (PRInt32 i = mObservers->Count() - 1; i >= 0; --i) {
             nsIRDFObserver* obs = (nsIRDFObserver*) mObservers->ElementAt(i);
             NS_RELEASE(obs);
         }