Merge branch 'bugfix/dangling_dce_when_init_fails' into 'master'

reset DCE pointer in DTE if we failed to init modem

Closes IDFGH-4936

See merge request espressif/esp-idf!12897

examples/protocols/pppos_client/components/modem/src/bg96.c

@@ -178,6 +178,7 @@ modem_dce_t *bg96_init(modem_dte_t *dte)
     return &(esp_modem_dce->parent);
 err_io:
     free(esp_modem_dce);
+    dte->dce = NULL;
 err:
     return NULL;
 }

examples/protocols/pppos_client/components/modem/src/sim800.c

@@ -176,6 +176,7 @@ modem_dce_t *sim800_init(modem_dte_t *dte)
     return &(esp_modem_dce->parent);
 err_io:
     free(esp_modem_dce);
+    dte->dce = NULL;
 err:
     return NULL;
 }