Shaders: Only convert default value to linear color if type is source_color

Author: beicause

servers/rendering/renderer_rd/storage_rd/material_storage.cpp

@@ -799,7 +799,7 @@ void MaterialStorage::MaterialData::update_uniform_buffer(const HashMap<StringNa
 
 		} else if (E.value.default_value.size()) {
 			//default value
-			_fill_std140_ubo_value(E.value.type, E.value.default_value, data, p_use_linear_color);
+			_fill_std140_ubo_value(E.value.type, E.value.default_value, data, E.value.hint == ShaderLanguage::ShaderNode::Uniform::HINT_SOURCE_COLOR && p_use_linear_color);
 			//value=E.value.default_value;
 		} else {
 			//zero because it was not provided