Merge pull request #1090 from microsoft/mk/fix-null-style-parameter-issue

Fix Reader always sets OpenApiParameter.Style

Author: MaggieKimani1

src/Microsoft.OpenApi/Models/OpenApiParameter.cs

@@ -239,9 +239,12 @@ public void SerializeAsV3WithoutReference(IOpenApiWriter writer)
 
             // allowEmptyValue
             writer.WriteProperty(OpenApiConstants.AllowEmptyValue, AllowEmptyValue, false);
-
+            
             // style
-            writer.WriteProperty(OpenApiConstants.Style, Style?.GetDisplayName());
+            if (_style.HasValue)
+            {
+                writer.WriteProperty(OpenApiConstants.Style, Style.Value.GetDisplayName());
+            }
 
             // explode
             writer.WriteProperty(OpenApiConstants.Explode, Explode, Style.HasValue && Style.Value == ParameterStyle.Form);