Couple of assertions

src/dawn/ui/UIComponent.cpp

@@ -8,6 +8,7 @@
 using namespace Dawn;
 
 UIComponent::UIComponent(UICanvas *canvas) {
+  assertNotNull(canvas);
   this->canvas = canvas;
 }
 
@@ -141,7 +142,7 @@ void UIComponent::addChild(UIComponent *child) {
 }
 
 void UIComponent::removeChild(UIComponent *child) {
-  if(child->parent != this) throw "Invalid child";
+  assertTrue(child->parent != this);
   auto it = this->children.begin();
   while(it != this->children.end()) {
     if(*it == child) {