Bug using BeginGroup within a Columns set

[ocornut]

Already fixed locally but posting with repro (so when we have testing system in place we can create tests for all those issues).

ImGui::Begin("Bug #630");
ImGui::Columns(2);

ImGui::BeginGroup();
ImGui::Text("Text 1");
ImGui::Text("Text 2");
ImGui::EndGroup();

ImGui::NextColumn();

ImGui::BeginGroup();
ImGui::Text("Text 3");
ImGui::Text("Text 4");
ImGui::EndGroup();

ImGui::Columns(1);
ImGui::End();