[orca] Prefer scrollSubstringTo over scrollTo for text objects

[Joanmarie Diggs <joanied src gnome org>]

commit d9ced9fd5e50a8d4e463059b5022959e192ed37b
Author: Joanmarie Diggs <jdiggs igalia com>
Date:   Tue Nov 19 10:17:39 2019 -0500

    Prefer scrollSubstringTo over scrollTo for text objects

 src/orca/eventsynthesizer.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)
---
diff --git a/src/orca/eventsynthesizer.py b/src/orca/eventsynthesizer.py
index a1791e8e7..418144f2a 100644
--- a/src/orca/eventsynthesizer.py
+++ b/src/orca/eventsynthesizer.py
@@ -221,11 +221,12 @@ def releaseAtPoint(x, y, button=1):
 def _scrollSubstringToLocation(obj, location, startOffset, endOffset):
     """Attemps to scroll the given substring to the specified location."""
 
-    if startOffset is None or endOffset is None:
-        return False
-
     try:
         text = obj.queryText()
+        if startOffset is None:
+            startOffset = 0
+        if endOffset is None:
+            endOffset = text.characterCount - 1
         result = text.scrollSubstringTo(startOffset, endOffset, location)
     except NotImplementedError:
         msg = "ERROR: Text interface not implemented for %s" % obj