tree-wide: check if non-empty password is acquired

(cherry picked from commit 204529d0fcde9a95119b489225620f36649c2f5b)
(cherry picked from commit e80e9dce63787d1d4494ed65d7c27018344387d5)
(cherry picked from commit a505f10)

src/home/homectl.c

@@ -1208,6 +1208,8 @@ static int acquire_new_password(
                 if (r < 0)
                         return log_error_errno(r, "Failed to acquire password: %m");
 
+                assert(!strv_isempty(first));
+
                 question = mfree(question);
                 if (asprintf(&question, "Please enter new password for user %s (repeat):", user_name) < 0)
                         return log_oom();

src/shared/dissect-image.c

@@ -2906,6 +2906,7 @@ int dissected_image_decrypt_interactively(
                 if (r < 0)
                         return log_error_errno(r, "Failed to query for passphrase: %m");
 
+                assert(!strv_isempty(z));
                 passphrase = z[0];
         }
 }

src/tty-ask-password-agent/tty-ask-password-agent.c

@@ -257,9 +257,7 @@ static int process_one_password_file(const char *filename) {
                         return log_error_errno(r, "Failed to query password: %m");
                 }
 
-                if (strv_isempty(passwords))
-                        return -ECANCELED;
-
+                assert(!strv_isempty(passwords));
                 r = send_passwords(socket_name, passwords);
                 if (r < 0)
                         return log_error_errno(r, "Failed to send: %m");