fix keyinfo null ref (#3203)

Author: jennyf19

src/Microsoft.IdentityModel.Xml/KeyInfo.cs

@@ -165,7 +165,7 @@ private bool Matches(X509SecurityKey key)
 
         private bool Matches(RsaSecurityKey key)
         {
-            if (key == null)
+            if (key == null || RSAKeyValue == null)
                 return false;
 
             if (!key.Parameters.Equals(default(RSAParameters)))

test/Microsoft.IdentityModel.Xml.Tests/KeyInfoTests.cs

@@ -334,6 +334,14 @@ public static TheoryData<KeyInfoTheoryData> KeyInfoMatchesTheoryData
                     MatchesKey = true,
                 });
 
+                theoryData.Add(new KeyInfoTheoryData("NullRSAKeyValue")
+                {
+                    ExpectedException = ExpectedException.NoExceptionExpected,
+                    KeyInfo = new KeyInfo(), // This will have null RSAKeyValue
+                    SecurityKey = KeyingMaterial.RsaSecurityKey_2048_Public,
+                    MatchesKey = false,
+                });
+
                 return theoryData;
             }
         }