SPR-9498: don't make assumptions about equality if ConversionService has failed

The failure of the conversion service is not fatal, but the check that
was in there (line 248) was inadequate to detect the cases that could
already be handled by the default property editors.  This code path
was also not tested anywhere in spring-beans tests until now.

spring-beans/src/test/java/org/springframework/beans/BeanWrapperTests.java

@@ -43,14 +43,16 @@ import java.util.TreeMap;
 import java.util.TreeSet;
 
 import org.apache.commons.logging.LogFactory;
-import org.junit.Ignore;
 import org.junit.Test;
 import org.springframework.beans.factory.annotation.Autowire;
 import org.springframework.beans.propertyeditors.CustomNumberEditor;
 import org.springframework.beans.propertyeditors.StringArrayPropertyEditor;
 import org.springframework.beans.propertyeditors.StringTrimmerEditor;
 import org.springframework.beans.support.DerivedFromProtectedBaseBean;
+import org.springframework.core.convert.ConversionFailedException;
+import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.support.DefaultConversionService;
+import org.springframework.core.convert.support.GenericConversionService;
 import org.springframework.util.StopWatch;
 import org.springframework.util.StringUtils;
 
@@ -66,9 +68,34 @@ import test.beans.TestBean;
  * @author Alef Arendsen
  * @author Arjen Poutsma
  * @author Chris Beams
+ * @author Dave Syer
  */
 public final class BeanWrapperTests {
 
+	@Test
+	public void testNullNestedTypeDescriptorWithNoConversionService() {
+		Foo foo = new Foo();
+		BeanWrapperImpl wrapper = new BeanWrapperImpl(foo);
+		wrapper.setAutoGrowNestedPaths(true);
+		wrapper.setPropertyValue("listOfMaps[0]['luckyNumber']", "9");
+		assertEquals("9", foo.listOfMaps.get(0).get("luckyNumber"));
+	}
+	
+	@Test
+	public void testNullNestedTypeDescriptorWithBadConversionService() {
+		Foo foo = new Foo();
+		BeanWrapperImpl wrapper = new BeanWrapperImpl(foo);
+		wrapper.setConversionService(new GenericConversionService() {
+			@Override
+			public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
+				throw new ConversionFailedException(sourceType, targetType, source, null);
+			}
+		});
+		wrapper.setAutoGrowNestedPaths(true);
+		wrapper.setPropertyValue("listOfMaps[0]['luckyNumber']", "9");
+		assertEquals("9", foo.listOfMaps.get(0).get("luckyNumber"));
+	}
+	
 	@Test
 	public void testNullNestedTypeDescriptor() {
 		Foo foo = new Foo();