Fix remap_parameter.

Need to return after backing variable resolve.
diff --git a/spirv_cross.cpp b/spirv_cross.cpp
index ef75204..30a189c 100644
--- a/spirv_cross.cpp
+++ b/spirv_cross.cpp
@@ -2324,13 +2324,13 @@
 
 uint32_t Compiler::CombinedImageSamplerHandler::remap_parameter(uint32_t id)
 {
-	if (parameter_remapping.empty())
-		return id;
-
 	auto *var = compiler.maybe_get_backing_variable(id);
 	if (var)
 		id = var->self;
 
+	if (parameter_remapping.empty())
+		return id;
+
 	auto &remapping = parameter_remapping.top();
 	auto itr = remapping.find(id);
 	if (itr != end(remapping))