crecord: throws error instead of crashing for large diffs

Before this patch, crecord was crashing for large diffs
(30k lines on my laptop). This patch catches the exception raised in that case
and use the error reporting mechanism introduced in the previous patch for
notifying the user of the issue. It is not possible to add a test for that for
now as we don't yet have full blown ui tests for the curses interface.

mercurial/crecord.py

@@ -1612,8 +1612,12 b' are you sure you want to review/edit and'
 
         # add 1 so to account for last line text reaching end of line
         self.numpadlines = self.getnumlinesdisplayed(ignorefolding=True) + 1
-        self.chunkpad = curses.newpad(self.numpadlines, self.xscreensize)
 
+        try:
+            self.chunkpad = curses.newpad(self.numpadlines, self.xscreensize)
+        except curses.error:
+            self.initerr = _('this diff is too large to be displayed')
+            return
         # initialize selecteitemendline (initial start-line is 0)
         self.selecteditemendline = self.getnumlinesdisplayed(
             self.currentselecteditem, recursechildren=False)