d3dx9: Fix D3DXMatrixStack_MultMatrixLocal to make tests pass in Windows.

dlls/d3dx9_36/math.c

@@ -866,7 +866,6 @@ static HRESULT WINAPI ID3DXMatrixStackImpl_MultMatrixLocal(ID3DXMatrixStack *ifa
 
     TRACE("iface %p\n", iface);
 
-    if (!pm) return D3DERR_INVALIDCALL;
     D3DXMatrixMultiply(&This->stack[This->current], pm, &This->stack[This->current]);
 
     return D3D_OK;

dlls/d3dx9_36/tests/math.c

@@ -1519,9 +1519,6 @@ static void test_matrix_stack(void)
     ok(SUCCEEDED(hr), "Pop failed, hr %#x\n", hr);
     ok(D3DXMatrixIsIdentity(ID3DXMatrixStack_GetTop(stack)), "The top should be an identity matrix\n");
 
-    hr = ID3DXMatrixStack_MultMatrixLocal(stack, NULL);
-    ok(hr == D3DERR_INVALIDCALL, "Expected D3DERR_INVALIDCALL, got %#x\n", hr);
-
     hr = ID3DXMatrixStack_RotateAxis(stack, NULL, 2.0f);
     ok(hr == D3DERR_INVALIDCALL, "Expected D3DERR_INVALIDCALL, got %#x\n", hr);