patch 8.2.1949: Vim9: using extend() on null dict is silently ignored

Problem:    Vim9: using extend() on null dict is silently ignored.
Solution:   Give an error message.  Initialize a dict variable with an empty
            dictionary. (closes #7251)

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1949,
 /**/
     1948,
 /**/