Rendering issue fix

Fixes ocornut/imgui#1172

imgui_draw.cpp

@@ -222,7 +222,7 @@ void ImDrawList::UpdateTextureID()
 
     // Try to merge with previous command if it matches, else use current command
     ImDrawCmd* prev_cmd = CmdBuffer.Size > 1 ? curr_cmd - 1 : NULL;
-    if (prev_cmd && prev_cmd->TextureId == curr_texture_id && memcmp(&prev_cmd->ClipRect, &GetCurrentClipRect(), sizeof(ImVec4)) == 0 && prev_cmd->UserCallback == NULL)
+    if (curr_cmd->ElemCount == 0 && prev_cmd && prev_cmd->TextureId == curr_texture_id && memcmp(&prev_cmd->ClipRect, &GetCurrentClipRect(), sizeof(ImVec4)) == 0 && prev_cmd->UserCallback == NULL)
         CmdBuffer.pop_back();
     else
         curr_cmd->TextureId = curr_texture_id;