style(clang-tidy): fix bugprone-unchecked-optional-access (#1762)

Signed-off-by: Balakrishna Avulapati <ba@bavulapati.com>
Co-authored-by: Juan Cruz Viotti <jv@jviotti.com>

Author: bavulapati

src/core/jsonschema/frame.cc

@@ -76,7 +76,11 @@ auto find_anchors(const sourcemeta::core::JSON &schema,
       const sourcemeta::core::URI identifier(schema.at("$id").to_string());
       if (identifier.is_fragment_only()) {
         result.insert(
-            {sourcemeta::core::JSON::String{identifier.fragment().value()},
+            {sourcemeta::core::JSON::String{
+                 identifier.fragment()
+                     .value()}, // NOLINT(bugprone-unchecked-optional-access):
+                                // Check for optional is happening
+                                // inside is_fragment_only()
              AnchorType::Static});
       }
     }
@@ -91,7 +95,11 @@ auto find_anchors(const sourcemeta::core::JSON &schema,
       const sourcemeta::core::URI identifier(schema.at("id").to_string());
       if (identifier.is_fragment_only()) {
         result.insert(
-            {sourcemeta::core::JSON::String{identifier.fragment().value()},
+            {sourcemeta::core::JSON::String{
+                 identifier.fragment()
+                     .value()}, // NOLINT(bugprone-unchecked-optional-access):
+                                // Check for optional is happening
+                                // inside is_fragment_only()
              AnchorType::Static});
       }
     }

src/core/jsonschema/walker.cc

@@ -47,7 +47,7 @@ auto walk(const std::optional<sourcemeta::core::Pointer> &parent,
   const auto current_base_dialect{
       is_schema_resource
           ? sourcemeta::core::base_dialect(subschema, resolver, current_dialect)
-                .value()
+                .value_or(base_dialect)
           : base_dialect};
 
   const auto vocabularies{sourcemeta::core::vocabularies(