richedit: Commit undo items after modifications in WM_IME_COMPOSITION.

ME_InsertTextFromCursor could previously follow the ME_CommitUndo call
leaving uncommitted changes which would cause improper grouping of commits,
or an assertion failure.
diff --git a/dlls/riched20/editor.c b/dlls/riched20/editor.c
index 7764614..e93db65 100644
--- a/dlls/riched20/editor.c
+++ b/dlls/riched20/editor.c
@@ -4256,7 +4256,6 @@
     ME_Style *style = ME_GetInsertStyle(editor, 0);
     hIMC = ITextHost_TxImmGetContext(editor->texthost);
     ME_DeleteSelection(editor);
-    ME_CommitUndo(editor);
     ME_SaveTempStyle(editor);
     if (lParam & GCS_RESULTSTR)
     {
@@ -4286,6 +4285,7 @@
                         editor->imeStartIndex + dwBufLen/sizeof(WCHAR));
     }
     ME_ReleaseStyle(style);
+    ME_CommitUndo(editor);
     ME_UpdateRepaint(editor);
     return 0;
   }