rpcrt4: Don't crash with a NULL binding handle in RpcBindingFree.

dlls/rpcrt4/rpc_binding.c

@@ -785,8 +785,11 @@ RPC_STATUS WINAPI RpcBindingFree( RPC_BINDING_HANDLE* Binding )
 {
   RPC_STATUS status;
   TRACE("(%p) = %p\n", Binding, *Binding);
-  status = RPCRT4_ReleaseBinding(*Binding);
-  if (status == RPC_S_OK) *Binding = 0;
+  if (*Binding)
+    status = RPCRT4_ReleaseBinding(*Binding);
+  else
+    status = RPC_S_INVALID_BINDING;
+  if (status == RPC_S_OK) *Binding = NULL;
   return status;
 }
   

dlls/rpcrt4/tests/rpc.c

@@ -800,6 +800,17 @@ static void test_UuidCreate(void)
     }
 }
 
+static void test_RpcBindingFree(void)
+{
+    RPC_BINDING_HANDLE binding = NULL;
+    RPC_STATUS status;
+
+    status = RpcBindingFree(&binding);
+    ok(status == RPC_S_INVALID_BINDING,
+       "RpcBindingFree should have retured RPC_S_INVALID_BINDING instead of %d\n",
+       status);
+}
+
 START_TEST( rpc )
 {
     UuidConversionAndComparison();
@@ -811,4 +822,5 @@ START_TEST( rpc )
     test_I_RpcExceptionFilter();
     test_RpcStringBindingFromBinding();
     test_UuidCreate();
+    test_RpcBindingFree();
 }