Document key spec null contracts (#557)

Refs #228

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: jonathanpeppers

docs/xml/Java.Security.Spec/EdECPrivateKeySpec.xml

@@ -92,6 +92,7 @@
         <param name="params">the algorithm parameters.</param>
         <param name="bytes">the key as a byte array. This array is copied
                          to protect against subsequent modification.</param>
+        <exception cref="T:Java.Lang.NullPointerException">if <c>params</c> or <c>bytes</c> is null.</exception>
         <summary>Construct a private key spec using the supplied parameters and
             bit string.</summary>
         <remarks>

docs/xml/Java.Security.Spec/EdECPublicKeySpec.xml

@@ -90,6 +90,7 @@
       <Docs>
         <param name="params">the algorithm parameters.</param>
         <param name="point">the point representing the public key.</param>
+        <exception cref="T:Java.Lang.NullPointerException">if <c>params</c> or <c>point</c> is null.</exception>
         <summary>Construct a public key spec using the supplied parameters and
             point.</summary>
         <remarks>

docs/xml/Java.Security.Spec/XECPrivateKeySpec.xml

@@ -91,6 +91,7 @@
         <param name="params">the algorithm parameters</param>
         <param name="scalar">the unpruned encoded scalar value. This array is copied
                           to protect against subsequent modification.</param>
+        <exception cref="T:Java.Lang.NullPointerException">if <c>params</c> or <c>scalar</c> is null.</exception>
         <summary>Construct a private key spec using the supplied parameters and
             encoded scalar value.</summary>
         <remarks>

docs/xml/Java.Security.Spec/XECPublicKeySpec.xml

@@ -91,6 +91,7 @@
         <param name="params">the algorithm parameters</param>
         <param name="u">the u-coordinate of the point, represented using a BigInteger
                      which may hold any value</param>
+        <exception cref="T:Java.Lang.NullPointerException">if <c>params</c> or <c>u</c> is null.</exception>
         <summary>Construct a public key spec using the supplied parameters and
             u coordinate.</summary>
         <remarks>