wmllint: fix a crash if advances_to= is placed before id= in [unit_type]

This was supposed to be a part of the fix for #4102, but for some reason it never got committed.

data/tools/wmllint

@@ -1587,26 +1587,22 @@ def global_sanity_check(filename, lines):
                 elif key == "hitpoints":
                     hitpoints_specified = True
                 elif key == "usage":
-                    assert(unit_id)
-                    usage[unit_id] = value
+                    unit_usage = value
                 elif key == "movement_type":
                     if '{' not in value:
-                        assert(unit_id)
-                        unit_movetypes.append((unit_id, filename, nav.lineno + 1, value))
+                        temp_movetypes.append((filename, nav.lineno + 1, value))
                     if value == "undeadspirit":
                         spirit_note_needed = True
                     elif value == "mounted":
                         defense_cap_note_needed = True
                 elif key == "race":
                     if '{' not in value:
-                        assert(unit_id or base_unit)
                         unit_race = value
-                        unit_races.append((unit_id, filename, nav.lineno + 1, unit_race))
+                        temp_races.append((filename, nav.lineno + 1, unit_race))
                 elif key == "advances_to":
-                    assert(unit_id or base_unit)
                     advancements = value
                     if advancements.strip() != "null":
-                        advances.append((unit_id, filename, nav.lineno + 1, advancements))
+                        temp_advances.append((filename, nav.lineno + 1, advancements))
                 elif key == "type" and value == "arcane" and "[attack]" in nav.ancestors():
                     arcane_note_needed = True
                 elif "[defense]" in nav.ancestors() and re.match(r"\-\d+",value):