fix: improve method body retrieval logic in InstructionPsiChangeListener

Author: PeyaPeyaPeyang

javasm-intellij-plugin/src/main/java/tokyo/peya/javasm/intellij/editor/linenumber/InstructionPsiChangeListener.java

@@ -47,7 +47,12 @@ private static void invalidateElement(@NotNull PsiElement element)
         if (!(element.getContainingFile() instanceof JALFile))
             return;
 
-        MethodBodyNode methodBody = PsiTreeUtil.getParentOfType(element, MethodBodyNode.class);
+        MethodBodyNode methodBody;
+        if (element instanceof MethodBodyNode)
+            methodBody = (MethodBodyNode) element;
+        else
+            methodBody = PsiTreeUtil.getParentOfType(element, MethodBodyNode.class);
+
         if (methodBody == null)
             return; // メソッドボディでない場合は無視