Convert blank strings to null for dates. Fixes #10007

Author: graemerocher

grails-databinding/src/main/groovy/org/grails/databinding/converters/DateConversionHelper.groovy

@@ -37,6 +37,9 @@ class DateConversionHelper implements ValueConverter {
     Object convert(value) {
         Date dateValue
         if (value instanceof String) {
+            if(!value) {
+                return null
+            }
             def firstException
             formatStrings.each { String format ->
                 if (dateValue == null) {

grails-databinding/src/main/groovy/org/grails/databinding/converters/FormattedDateValueConverter.groovy

@@ -31,9 +31,17 @@ class FormattedDateValueConverter implements FormattedValueConverter {
         if(value instanceof Date) {
             return value
         }
-        def fmt = new SimpleDateFormat(format)
-        fmt.lenient = false
-        fmt.parse((String) value)
+        else if(value instanceof CharSequence) {
+            String dateStr = value.toString()
+            if(!dateStr) {
+                return null
+            }
+            else {
+                def fmt = new SimpleDateFormat(format)
+                fmt.lenient = false
+                fmt.parse((String) value)
+            }
+        }
     }
 
     Class<?> getTargetType() {

grails-databinding/src/test/groovy/org/grails/databinding/converters/DateConversionHelperSpec.groovy

@@ -77,9 +77,20 @@ class DateConversionHelperSpec extends Specification {
         def helper = new DateConversionHelper()
 
         when:
-        helper.convert ''
+        def date = helper.convert ''
 
         then:
-        thrown ParseException
+        date == null
+    }
+
+    void 'Test formatted an empty String'() {
+        given:
+        def helper = new FormattedDateValueConverter()
+
+        when:
+        def date = helper.convert '', "yyMMdd"
+
+        then:
+        date == null
     }
 }