8180576: Null pointer dereference in Matcher::xform()

Summary: Fixed a missing null check on n->in(0) found by Parfait.
Reviewed-by: kvn

src/share/vm/opto/matcher.cpp

@@ -1020,7 +1020,7 @@ Node *Matcher::xform( Node *n, int max_stack ) {
             if (C->failing())  return NULL;
             if (m == NULL) { Matcher::soft_match_failure(); return NULL; }
           } else {                  // Nothing the matcher cares about
-            if( n->is_Proj() && n->in(0)->is_Multi()) {       // Projections?
+            if (n->is_Proj() && n->in(0) != NULL && n->in(0)->is_Multi()) {       // Projections?
               // Convert to machine-dependent projection
               m = n->in(0)->as_Multi()->match( n->as_Proj(), this );
 #ifdef ASSERT