Use .TryGetValue() when we expect the key might not exist.

Author: StephenMolloy

src/Json/SimpleJsonConfigBuilder.cs

@@ -142,8 +142,8 @@ private Dictionary<string, string> GetCurrentDictionary()
         {
             if (JsonMode == SimpleJsonConfigBuilderMode.Sectional && _currentSection != null)
             {
-                Dictionary<string, string> d = _allSettings[_currentSection];
-                return d ?? _allSettings[""];
+                if (_allSettings.TryGetValue(_currentSection, out Dictionary<string, string> d))
+                    return d;
             }
 
             return _allSettings[""];