The effect of this part shall be that no contract or undertaking entered into by any person, firm, or corporation, whether heretofore or hereafter entered into, shall be invalidated or declared illegal on the ground that the same was entered into in a trade or partnership name not filed or registered in accordance with the laws in force at the time such contract or undertaking was entered into; but all such contracts and undertakings are expressly validated as against any such objection; and no action heretofore or hereafter instituted by any such person, firm, partnership, or corporation, whether sounding in contract or tort, shall be defeated because of any such failure to register. But the party who has failed to register his trade or partnership name at the time action is filed, as required by this part, shall be cast with court costs.