vim-patch:8.1.1259: crash when exiting early (neovim#35552)

Problem:    Crash when exiting early. (Ralf Schandl)
Solution:   Only pop/push the title when it was set. (closes vim/vim#4334)

vim/vim@e5c8328

Co-authored-by: Bram Moolenaar <[email protected]>

Author: janlazo

src/nvim/memory.c

@@ -863,7 +863,7 @@ void free_all_mem(void)
 
   // Close all tabs and windows.  Reset 'equalalways' to avoid redraws.
   p_ea = false;
-  if (first_tabpage->tp_next != NULL) {
+  if (first_tabpage != NULL && first_tabpage->tp_next != NULL) {
     do_cmdline_cmd("tabonly!");
   }
 
@@ -873,18 +873,20 @@ void free_all_mem(void)
   // Clear user commands (before deleting buffers).
   ex_comclear(NULL);
 
-  // Clear menus.
-  do_cmdline_cmd("aunmenu *");
-  do_cmdline_cmd("tlunmenu *");
-  do_cmdline_cmd("menutranslate clear");
+  if (curbuf != NULL) {
+    // Clear menus.
+    do_cmdline_cmd("aunmenu *");
+    do_cmdline_cmd("tlunmenu *");
+    do_cmdline_cmd("menutranslate clear");
 
-  // Clear mappings, abbreviations, breakpoints.
-  // NB: curbuf not used with local=false arg
-  map_clear_mode(curbuf, MAP_ALL_MODES, false, false);
-  map_clear_mode(curbuf, MAP_ALL_MODES, false, true);
-  do_cmdline_cmd("breakdel *");
-  do_cmdline_cmd("profdel *");
-  do_cmdline_cmd("set keymap=");
+    // Clear mappings, abbreviations, breakpoints.
+    // NB: curbuf not used with local=false arg
+    map_clear_mode(curbuf, MAP_ALL_MODES, false, false);
+    map_clear_mode(curbuf, MAP_ALL_MODES, false, true);
+    do_cmdline_cmd("breakdel *");
+    do_cmdline_cmd("profdel *");
+    do_cmdline_cmd("set keymap=");
+  }
 
   free_titles();
   free_findfile();
@@ -905,7 +907,9 @@ void free_all_mem(void)
   free_cd_dir();
   free_signs();
   set_expr_line(NULL);
-  diff_clear(curtab);
+  if (curtab != NULL) {
+    diff_clear(curtab);
+  }
   clear_sb_text(true);            // free any scrollback text
 
   // Free some global vars.
@@ -922,8 +926,10 @@ void free_all_mem(void)
   // Close all script inputs.
   close_all_scripts();
 
-  // Destroy all windows.  Must come before freeing buffers.
-  win_free_all();
+  if (curwin != NULL) {
+    // Destroy all windows.  Must come before freeing buffers.
+    win_free_all();
+  }
 
   // Free all option values.  Must come after closing windows.
   free_all_options();
@@ -957,8 +963,10 @@ void free_all_mem(void)
 
   reset_last_sourcing();
 
-  free_tabpage(first_tabpage);
-  first_tabpage = NULL;
+  if (first_tabpage != NULL) {
+    free_tabpage(first_tabpage);
+    first_tabpage = NULL;
+  }
 
   // message history
   msg_hist_clear(0);

src/nvim/tag.c

@@ -2453,7 +2453,9 @@ static bool found_tagfile_cb(int num_fnames, char **fnames, bool all, void *cook
 void free_tag_stuff(void)
 {
   ga_clear_strings(&tag_fnames);
-  do_tag(NULL, DT_FREE, 0, 0, 0);
+  if (curwin != NULL) {
+    do_tag(NULL, DT_FREE, 0, 0, 0);
+  }
   tag_freematch();
 
   tagstack_clear_entry(&ptag_entry);

src/nvim/usercmd.c

@@ -1053,7 +1053,9 @@ void ex_command(exarg_T *eap)
 void ex_comclear(exarg_T *eap)
 {
   uc_clear(&ucmds);
-  uc_clear(&curbuf->b_ucmds);
+  if (curbuf != NULL) {
+    uc_clear(&curbuf->b_ucmds);
+  }
 }
 
 void free_ucmd(ucmd_T *cmd)