Fix potential race condition in Lazy.getNullable().

The getNullable() method had a subtle race condition where the value field
could be read as null after being assigned but before the resolved flag was
set to true. This could occur if another thread read the value between lines
136 and 137.

This change maintains the existing behavior documented in the class Javadoc
that the supplier may be called multiple times under concurrent access, while
fixing the potential for incorrect null returns.

Signed-off-by: jbj338033 <jbj338033@gmail.com>
Closes #3368

Author: jbj338033

src/main/java/org/springframework/data/util/Lazy.java

@@ -133,10 +133,11 @@ public T getNullable() {
 			return value;
 		}
 
-		this.value = supplier.get();
+		T result = supplier.get();
+		this.value = result;
 		this.resolved = true;
 
-		return value;
+		return result;
 	}
 
 	/**