When the OK button in the component preset dialog is pressed without selecting an item, don't change the current preset for the component. This was reported as an IndexOutOfBounds exception.

core/src/net/sf/openrocket/gui/dialogs/preset/ComponentPresetChooserDialog.java

@@ -238,6 +238,10 @@ public class ComponentPresetChooserDialog extends JDialog {
 		if (!okClicked)
 			return null;
 		int row = componentSelectionTable.getSelectedRow();
+		if ( row < 0 ) {
+			// Nothing selected.
+			return null;
+		}
 		row = componentSelectionTable.convertRowIndexToModel(row);
 		return presets.get(row);
 	}