use mutex to avoid window destroy deadlock, fix vertical slider to increase value upward

src/node_panel_color.cpp

@@ -46,7 +46,7 @@ void NodePanelColor::init_controls()
 void NodePanelColor::set_color(glm::vec3 rgb)
 {
     auto hsv = convert_rgb2hsv(rgb);
-    m_hue->m_value.y = hsv.x;
+    m_hue->m_value = hsv.x;
     m_quad->m_value = glm::vec2(hsv.y, 1.f - hsv.z);
     m_quad->m_color = glm::vec4(rgb, 1);
     m_cursor = m_quad->m_value;