winex11: Make sure HIMC is opened before sending IME updates.

dlls/winex11.drv/xim.c

@@ -175,6 +175,7 @@ static int xic_preedit_start( XIC xic, XPointer user, XPointer arg )
     if ((ime_comp_buf = realloc( ime_comp_buf, sizeof(WCHAR) ))) *ime_comp_buf = 0;
     else ERR( "Failed to allocate preedit buffer\n" );
 
+    NtUserPostMessage( hwnd, WM_IME_NOTIFY, IMN_WINE_SET_OPEN_STATUS, TRUE );
     post_ime_update( hwnd, 0, ime_comp_buf, NULL );
 
     return -1;
@@ -190,6 +191,7 @@ static int xic_preedit_done( XIC xic, XPointer user, XPointer arg )
     ime_comp_buf = NULL;
 
     post_ime_update( hwnd, 0, NULL, NULL );
+    NtUserPostMessage( hwnd, WM_IME_NOTIFY, IMN_WINE_SET_OPEN_STATUS, FALSE );
 
     return 0;
 }