Fix SetNextWindowContentSize() with 0.0f on Y axis (or SetNextWindowContentWidth()) overwriting the contents size. Broken in eab6333a0b. (#1363)

imgui.cpp

@@ -4544,6 +4544,7 @@ bool ImGui::Begin(const char* name, bool* p_open, ImGuiWindowFlags flags)
     {
         // Adjust passed "client size" to become a "window size"
         window->SizeContentsExplicit = g.NextWindowData.ContentSizeVal;
+        if (window->SizeContentsExplicit.y != 0.0f)
             window->SizeContentsExplicit.y += window->TitleBarHeight() + window->MenuBarHeight();
         g.NextWindowData.ContentSizeCond = 0;
     }