app_voicemail: Fix test_voicemail_notify_endl test.

The test_voicemail_notify_endl test checks the end-of-line
characters of an email message to confirm that they are consistent.
The test wrongfully assumed that reading from the email message
into a buffer will always result in more than 1 character being
read. This is incorrect. If only 1 character was read the test
would go outside of the buffer and access other memory causing
a crash.

The test now checks to ensure that 2 or more characters are read
in ensuring the test stays within the buffer.

ASTERISK-25874 #close

Change-Id: Ic2c89cea6e90f2c0bc2d8138306ebbffd4f8b710

apps/app_voicemail.c

@@ -14456,11 +14456,13 @@ AST_TEST_DEFINE(test_voicemail_notify_endl)
 		rewind(file);
 		while (fgets(buf, sizeof(buf), file)) {
 			if (
+			(strlen(buf) > 1 &&
 #ifdef IMAP_STORAGE
 			buf[strlen(buf) - 2] != '\r'
 #else
 			buf[strlen(buf) - 2] == '\r'
 #endif
+			)
 			|| buf[strlen(buf) - 1] != '\n') {
 				res = AST_TEST_FAIL;
 			}