fix(gui): Skip empty strings in selectable to prevent ImGui ID assertion

Empty strings in bias_profiles.keys() and personas.keys() caused
imgui.selectable() to fail with 'Cannot have an empty ID at root of
window' assertion error. Added guards to skip empty names.

src/gui_2.py

@@ -2652,6 +2652,8 @@ def hello():
    if imgui.selectable("None", not self.ui_active_persona)[0]:
     self.ui_active_persona = ""
    for pname in sorted(personas.keys()):
+    if not pname:
+     continue
     if imgui.selectable(pname, pname == self.ui_active_persona)[0]:
      self.ui_active_persona = pname
      if pname in personas:
@@ -4219,6 +4221,8 @@ def hello():
      from src import ai_client
      ai_client.set_bias_profile(None)
     for bname in sorted(self.controller.bias_profiles.keys()):
+     if not bname:
+      continue
      if imgui.selectable(bname, bname == getattr(self, 'ui_active_bias_profile', ""))[0]:
       self.ui_active_bias_profile = bname
       from src import ai_client