Fix typecheck errors

https://github.com/hayat01sh1da/json-data-sorters/actions/runs/26411739646/job/77747485985?pr=61

Author: hayat01sh1da

ruby/src/application.rb

@@ -66,7 +66,7 @@ def run
 
   # @rbs return: Hash[String, untyped]?
   def json_data
-    File.open(filepath) { |f| JSON.parse(f) }
+    File.open(filepath) { |f| JSON.parse(f.read) }
   end
 
   # @rbs return: Hash[String, untyped]?
@@ -99,7 +99,10 @@ def sort_value(value)
 
   # @rbs return: bool
   def test_env?
-    caller(0..0).first.split('/').last.include?('minitest.rb')
+    runner = caller(0..0)
+    return false if runner.nil?
+
+    runner.first.split('/').last.include?('minitest.rb')
   end
 
   # @rbs message: String

ruby/test/application_test.rb

@@ -63,7 +63,7 @@ def test_sort_json_data_with_invalid_data_type_of_order
   attr_reader :dirname, :filename, :filepath
 
   def actual_json
-    File.open(filepath) { |f| JSON.parse(f).deep_symbolize_keys }
+    File.open(filepath) { |f| JSON.parse(f.read).deep_symbolize_keys }
   end
 
   def json_data