Make fomod matching logic work in more cases

Some mods (like Water for ENB) expect to disqualify a potential plugin
from inclusion when user selections cause that flag to be absent.

This has been fixed, so Water for ENB (and any other fomods that work
like this) are functioning properly now when used with the 'configure'
command.

ammo/fomod_controller.py

@@ -263,6 +263,9 @@ def _flags_match(self, flags: dict, operator=None) -> bool:
                     continue
                 # A single match.
                 match = True
+            elif operator == "and":
+                # Missing flags counts as failure for 'and'.
+                return False
         return match
 
     def _select(self, index: int) -> None:
@@ -342,11 +345,10 @@ def _get_nodes(self) -> list[ElementTree.Element]:
                 # can't find files for this, no point in checking whether to include.
                 continue
 
-            if not dependency:
+            if not dependency.flags:
                 # No requirements for these files to be used.
                 selected_nodes.extend(xml_files)
-
-            if self._flags_match(dependency.flags, dependency.operator):
+            elif self._flags_match(dependency.flags, dependency.operator):
                 selected_nodes.extend(xml_files)
 
         xml_required_files = self.xml_root_node.find("requiredInstallFiles") or []