updated for version 7.3.361

Problem:    Accessing memory after it is freed when EXITFREE is defined.
Solution:   Don't access curwin when firstwin is NULL. (Dominique Pelle)

src/buffer.c

@@ -567,8 +567,9 @@ buf_freeall(buf, flags)
     diff_buf_delete(buf);	    /* Can't use 'diff' for unloaded buffer. */
 #endif
 #ifdef FEAT_SYN_HL
-    if (curwin->w_buffer == buf)
-	reset_synblock(curwin);	    /* remove any ownsyntax */
+    /* Remove any ownsyntax, unless exiting. */
+    if (firstwin != NULL && curwin->w_buffer == buf)
+	reset_synblock(curwin);
 #endif
 
 #ifdef FEAT_FOLDING