HPCC-17619 Internal error from the regression suite engine

Fix the bug what caused Regression Test Engine crash when an empty value
comes from a queryxml file.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>

testing/regress/hpcc/util/ecl/file.py

@@ -169,7 +169,10 @@ class ECLFile:
             root = tree.getroot()
             for child in root:
                 key = '-X'+child.tag
-                val = child.text
+                if child.text != None:
+                    val = child.text
+                else:
+                    val =''
                 retHash[key] = val
             pass
         logging.debug("%3d. checkQueryxmlFile() returns with %s stored parameter(s) ",  self.taskId,  len(retHash) )