input using 'alt gr' not working on linux

on german keyborads you need alt gr for some essential chars ('{', '[', etc..).
(maybe related: ocornut/imgui#334)
diff --git a/TextEditor.cpp b/TextEditor.cpp
index cddb6ca..1f03e9c 100644
--- a/TextEditor.cpp
+++ b/TextEditor.cpp
@@ -518,7 +518,7 @@
 			EnterCharacter('\n', false);

 		else if (!IsReadOnly() && !ctrl && !alt && ImGui::IsKeyPressed(ImGui::GetKeyIndex(ImGuiKey_Tab)))

 			EnterCharacter('\t', shift);

-		else if (!IsReadOnly() && !ctrl && !alt)

+		else if (!IsReadOnly() && !ctrl)

 		{

 			for (int i = 0; i < io.InputQueueCharacters.Size; i++)

 			{