fix(entitybrowser): Null GameEntitySystem (#6)

Author: skuzzis

src/imgui/panels/entitybrowser/entitybrowser.cpp

@@ -60,22 +60,24 @@ void Draw(bool* isOpen)
 		ImGui::TableHeadersRow();
 
 		EntityInstanceIter_t iter;
-
-		while (CEntityInstance* entity = iter.Next())
+		if(GameEntitySystem())
 		{
-			if (!g_menuContext.m_entityFilter.PassFilter(entity->GetClassname()))
-				continue;
-
-			ImGui::TableNextRow();
-			ImGui::TableSetColumnIndex(0);
-			ImGui::PushID(entity->GetEntityIndex().Get());
-			if (ImGui::Selectable(entity->GetClassname(), false, ImGuiSelectableFlags_SpanAllColumns))
+			while (CEntityInstance* entity = iter.Next())
 			{
-				g_pSelectedEntity = entity->GetRefEHandle();
+				if (!g_menuContext.m_entityFilter.PassFilter(entity->GetClassname()))
+					continue;
+
+				ImGui::TableNextRow();
+				ImGui::TableSetColumnIndex(0);
+				ImGui::PushID(entity->GetEntityIndex().Get());
+				if (ImGui::Selectable(entity->GetClassname(), false, ImGuiSelectableFlags_SpanAllColumns))
+				{
+					g_pSelectedEntity = entity->GetRefEHandle();
+				}
+				ImGui::PopID();
+				ImGui::TableSetColumnIndex(1);
+				ImGui::Text("%d", entity->GetEntityIndex());
 			}
-			ImGui::PopID();
-			ImGui::TableSetColumnIndex(1);
-			ImGui::Text("%d", entity->GetEntityIndex());
 		}
 
 		ImGui::EndTable();