fix: potential NullPointerException in Value#hashCode (googleapis#4046)

The Value#hashCode() method throwed a NullPointerException for untyped values.

Author: olavloite

google-cloud-spanner/src/main/java/com/google/cloud/spanner/Value.java

@@ -1716,7 +1716,10 @@ public final int hashCode() {
        * while calculating valueHash of Float32 type. Note that this is not applicable for composite
        * types containing FLOAT32.
        */
-      if (type.getCode() == Type.Code.FLOAT32 && !isNull && Float.isNaN(getFloat32())) {
+      if (type != null
+          && type.getCode() == Type.Code.FLOAT32
+          && !isNull
+          && Float.isNaN(getFloat32())) {
         typeToHash = Type.float64();
       }
 

google-cloud-spanner/src/test/java/com/google/cloud/spanner/ValueTest.java

@@ -94,6 +94,8 @@ public void untyped() {
     assertNull(v.getType());
     assertFalse(v.isNull());
     assertSame(proto, v.toProto());
+    assertNotEquals(0, v.hashCode());
+    assertEquals(v, Value.untyped(proto));
 
     assertEquals(
         v, Value.untyped(com.google.protobuf.Value.newBuilder().setStringValue("test").build()));