Check return value of fread()

src/sbbs3/mailsrvr.c

@@ -3717,7 +3717,9 @@ static void smtp_thread(void* arg)
 					subnum=INVALID_SUB;
 					continue;
 				}
-				fread(msgbuf,(size_t)length,1,msgtxt);
+				if(fread(msgbuf,(size_t)length,1,msgtxt) != 1)
+					*msgbuf = '\0';
+				else
 					msgbuf[length]=0;	/* ASCIIZ */
 
 				/* Do external JavaScript processing here? */