Fix aapt2 JavaClassGenerator Maybe#value() call before check

Previous refactor accidentally assumed all attributes would have
resolvable symbols when generating the R class. Restore previous
behavior of calling SkipSymbol before retrieving the attribute
comment.

Bug: 145685954
Test: m TeleService
Change-Id: Ie8e1092556bc0b6a764462ffa0b99a876bcbd70e
diff --git a/tools/aapt2/java/JavaClassGenerator.cpp b/tools/aapt2/java/JavaClassGenerator.cpp
index 31d205e..5b90d8d 100644
--- a/tools/aapt2/java/JavaClassGenerator.cpp
+++ b/tools/aapt2/java/JavaClassGenerator.cpp
@@ -304,9 +304,11 @@
     auto documentation_remove_iter = std::remove_if(documentation_attrs.begin(),
                                                     documentation_attrs.end(),
                                                     [&](StyleableAttr entry) -> bool {
-      StringPiece attr_comment_line = entry.symbol.value().attribute->GetComment();
-      return SkipSymbol(entry.symbol) || attr_comment_line.contains("@removed")
-                                      || attr_comment_line.contains("@hide");
+      if (SkipSymbol(entry.symbol)) {
+        return true;
+      }
+      const StringPiece attr_comment_line = entry.symbol.value().attribute->GetComment();
+      return attr_comment_line.contains("@removed") || attr_comment_line.contains("@hide");
     });
     documentation_attrs.erase(documentation_remove_iter, documentation_attrs.end());