#220 - Polishing.

Reverted removal of null check that is marked as superfluous and adjusted nullability annotations instead.

Author: schauder

Diff for: src/main/java/org/springframework/data/r2dbc/core/DefaultStatementMapper.java

@@ -188,7 +188,7 @@ private PreparedOperation<Update> getMappedObject(UpdateSpec updateSpec,
 		BindMarkers bindMarkers = this.dialect.getBindMarkersFactory().create();
 		Table table = Table.create(toSql(updateSpec.getTable()));
 
-		if (updateSpec.getUpdate().getAssignments().isEmpty()) {
+		if (updateSpec.getUpdate() == null || updateSpec.getUpdate().getAssignments().isEmpty()) {
 			throw new IllegalArgumentException("UPDATE contains no assignments");
 		}
 

Diff for: src/main/java/org/springframework/data/r2dbc/core/StatementMapper.java

@@ -460,11 +460,12 @@ public Map<SqlIdentifier, SettableValue> getAssignments() {
 	class UpdateSpec {
 
 		private final SqlIdentifier table;
+		@Nullable
 		private final Update update;
 
 		private final @Nullable Criteria criteria;
 
-		protected UpdateSpec(SqlIdentifier table, Update update, @Nullable Criteria criteria) {
+		protected UpdateSpec(SqlIdentifier table, @Nullable Update update, @Nullable Criteria criteria) {
 
 			this.table = table;
 			this.update = update;
@@ -506,6 +507,7 @@ public SqlIdentifier getTable() {
 			return this.table;
 		}
 
+		@Nullable
 		public Update getUpdate() {
 			return this.update;
 		}