Its now impossible to have empty forms

reading_machine/src/Action.cpp

@@ -386,7 +386,15 @@ Action Action::addCurCharToCurWord()
 
   auto appliable = [](const Config & config, const Action &)
   {
-    return config.hasCharacter(config.getCharacterIndex()) and !util::isIllegal(config.getLetter(config.getCharacterIndex()));
+    if (!config.hasCharacter(config.getCharacterIndex()))
+      return false;
+
+    auto letter = config.getLetter(config.getCharacterIndex());
+
+    if (letter == ' ')
+      return !util::isEmpty(config.getAsFeature("FORM", config.getWordIndex()));
+
+    return !util::isIllegal(letter);
   };
 
   return {Type::Write, apply, undo, appliable};