fexc: Don't fail silently on parse error

A test case for this is "fex2bin a-star_kv49l.fex".

This patch fixes an execution path in script_fex.c that would
allow script_parse_fex() to fail (i.e. return 0) without providing
any feedback to the user.
Signed-off-by: Bernhard Nortmann <bernhard.nortmann@web.de>

script_fex.c

@@ -344,6 +344,8 @@ int script_parse_fex(FILE *in, const char *filename, struct script *script)
 			} else {
 				goto invalid_char_at_p;
 			}
+			errf("E: %s:%zu: parse error at %zu.\n",
+			     filename, line, p-buffer+1);
 			goto parse_error;
 invalid_char_at_p:
 			errf("E: %s:%zu: invalid character at %zu.\n",