Exit upon failure to open attachment.

Error out properly if we cannot open a file to attach.

src/fmail.c

@@ -141,7 +141,9 @@ check_7bit_encoding(const char *filename)
     int c, ok = 1;
     unsigned n;
 
-    f = fopen(filename, "r");
+    if ( ! (f = fopen(filename, "r")) )
+        return 0;   /* We'll error out later. */
+
     while ( ! feof(f) && ! ok ) {
         c = fgetc(f);
 
@@ -609,7 +611,9 @@ process_attachment(const char *filename, magic_t ctx, FILE *out)
     fprintf(out, "Content-Transfer-Encoding: %s\r\n", encoding_names[encoding]);
     fprintf(out, "Content-Disposition: attachment; filename=%s\r\n\r\n", get_basename(filename));
 
-    f = fopen(filename, "r");
+    if ( ! (f = fopen(filename, "r")) )
+        err(EXIT_FAILURE, "cannot open attachment '%s'", filename);
+
     encoding_funcs[encoding](f, out);
     fclose(f);