tpm2_clockrateadjust: Fix segfault.

tpm2_clockrateadjust did produce a segfault if no rate adjust specifier was used.
Fixes: #3494x

Signed-off-by: Juergen Repp <juergen_repp@web.de>

Author: JuergenReppSIT

tools/tpm2_clockrateadjust.c

@@ -39,6 +39,7 @@ struct tpm2_setclock_ctx {
 static tpm2_setclock_ctx ctx = {
     .auth_hierarchy.ctx_path = "o", /* default to owner hierarchy */
     .parameter_hash_algorithm = TPM2_ALG_ERROR,
+    .adjustment = NULL,
 };
 
 
@@ -143,6 +144,11 @@ static tool_rc check_options(ESYS_CONTEXT *ectx) {
 
     UNUSED(ectx);
 
+    if (!ctx.adjustment) {
+        LOG_ERR("No clock rate adjust specifier is used");
+        return tool_rc_option_error;
+    }
+
     size_t len = strlen(ctx.adjustment);
     if (len > 3) {
         LOG_ERR("Expected at most 3 adjustment characters");