patch 8.2.3942: Coverity reports a possible memory leak

Problem:    Coverity reports a possible memory leak.
Solution:   Free the array if allocation fails.

src/insexpand.c

@@ -3193,6 +3193,8 @@ get_next_spell_completion(linenr_T lnum UNUSED)
     num_matches = expand_spelling(lnum, compl_pattern, &matches);
     if (num_matches > 0)
 	ins_compl_add_matches(num_matches, matches, p_ic);
+    else
+	vim_free(matches);
 #endif
 }
 

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3942,
 /**/
     3941,
 /**/