ldml.LocaleScanner.__find(): only Error if no matches found

The existing caller returns early on finding a match, so never ran off
the end of the iteration unless there were no matches. I'll soon be
adding a new caller that wants to iterate all matches, so will run off
the end even when there are some. So only raise the Error if we found
nothing.

Task-number: QTBUG-115158
Change-Id: I1cae4674eb5e83c433554c15ecc4441b756f20eb
Reviewed-by: Cristian Maureira-Fredes <cristian.maureira-fredes@qt.io>

util/locale_database/ldml.py

@@ -413,7 +413,7 @@ class LocaleScanner (object):
         ) # Used for month and day names
 
     def __find(self, xpath):
-        retries = [ xpath.split('/') ]
+        retries, foundNone = [ xpath.split('/') ], True
         while retries:
             tags, elts, roots = retries.pop(), self.nodes, (self.base.root,)
             for selector in tags:
@@ -423,6 +423,8 @@ class LocaleScanner (object):
                     break
 
             else: # Found matching elements
+                if elts:
+                    foundNone = False
                 # Possibly filter elts to prefer the least drafty ?
                 for elt in elts:
                     yield elt
@@ -442,15 +444,19 @@ class LocaleScanner (object):
                 if not roots:
                     if retries: # Let outer loop fall back on an alias path:
                         break
+                    if foundNone:
                         sought = '/'.join(tags)
                         if sought != xpath:
                             sought += f' (for {xpath})'
                         raise Error(f'All lack child {selector} for {sought} in {self.name}')
 
             else: # Found matching elements
+                if roots:
+                    foundNone = False
                 for elt in roots:
                     yield elt
 
+        if foundNone:
             sought = '/'.join(tags)
             if sought != xpath:
                 sought += f' (for {xpath})'