Creating a window after a modal popup causes an assert (1.86 release)

[ET3D-ET3D]

Here's a simple example:

		ImGui::OpenPopup("Popup");
		if (ImGui::BeginPopupModal("Popup", NULL, ImGuiWindowFlags_AlwaysAutoResize))
		{
			ImGui::Text("In popup");
			ImGui::EndPopup();
		}

		ImGui::Begin("Window");
		ImGui::Text("Test");
		ImGui::End();

This asserts in the Begin function of the window on "IM_ASSERT(blocking_modal != NULL);".

I fixed it locally by replacing the assert with

		if (blocking_modal == NULL)
			blocking_modal = modal;

I don't understand the code deeply enough to know if this is the best fix, but it seems to work well.

[ocornut]

Thank you @ET3D-ET3D for reporting.
@rokups looked at it and pushed a fix 19471da

(Also added a regression test for it)

[ET3D-ET3D]

Impressively quick response. Thanks.