Adding existing tracked files from a git submodule should not trigger the "Add to version control" dialog

When adding existing files (tracked by git) to a project (through the project pane > right mouse click -> add existing files menu) from a subfolder where a git submodule is present, the showing of the "Add to version control" dialog is unnecessary.

In the case if the added file is not tracked by git then the dialog is still relevant, and the current behaviour does the correct action (adds the file to the submodule).