HLSL: Fix #902: Incorrect protection against zero arguments.

Test/hlsl.function.frag

@@ -0,0 +1,25 @@
+float4 fun0()
+{
+    return 1.0f;
+}
+
+uint fun2(float4 col)
+{
+    return 7;
+}
+
+float4 fun4(uint id1, uint id2)
+{
+    return id1 * id2;
+}
+
+float4 fun1(int index)
+{
+    uint entityId = fun2(fun0());
+    return fun4(entityId, entityId);
+}
+
+int main() : SV_TARGET
+{
+    return fun1;
+}