Section 57A. A defendant shall not be discharged for want of jurisdiction if the evidence discloses that the crime with which he is charged was actually committed without the county or the territorial jurisdiction of the court in which he is being tried; provided, that the attorney general or the district attorney petitions to the court before proceeding with the trial for leave to proceed, stating that he is in doubt from the state of the evidence then in his possession as to whether or not the crime was committed within the county or the territorial jurisdiction of the court, and the court after hearing said petition orders the trial to proceed.