Bad calibration export when estimate K4 parameters in metashape or index not found if not estimate unused K3 parameter

[Peamon]

Hi, when you export camera parameters you use an index but, if you calculate K4 for example in metashape, the index are not correct anymore. I propose this change in the code to be sure having no problem. it will also create a better error message when camera parameters that is needed is not present in xml file.

Replace at line 113:

		fl_x = float(calibration[1].text)
		fl_y = fl_x
		k1 = float(calibration[4].text)
		k2 = float(calibration[5].text)
		p1 = float(calibration[7].text)
		p2 = float(calibration[8].text)
		cx = float(calibration[2].text) + w/2
		cy = float(calibration[3].text) + h/2

By:

		for chld in calibration:
			if chld.tag == "f":
				fl_x = float(chld.text)
				fl_y = fl_x
			elif chld.tag == "cx":
				cx = float(chld.text) + w/2
			elif chld.tag == "cy":
				cy = float(chld.text) + h/2
			elif chld.tag == "k1":
				k1 = float(chld.text)
			elif chld.tag == "k2":
				k2 = float(chld.text)
			elif chld.tag == "p1":
				p1 = float(chld.text)
			elif chld.tag == "p2":
				p2 = float(chld.text)

Agisoft export with only k1 k2 estimated is like this:

        <calibration type="frame" class="adjusted">
          <resolution width="540" height="960"/>
          <f>768.68340771397811</f>
          <cx>-10.291821702893024</cx>
          <cy>3.7142687950142763</cy>
          <k1>0.054258424223576199</k1>
          <k2>-0.1179548245864302</k2>
          <p1>-0.0011294399122456702</p1>
          <p2>0.0022433983854041159</p2>
        </calibration>

Agisoft export with k3 and k4 estimated is like this:

        <calibration type="frame" class="adjusted">
          <resolution width="540" height="960"/>
          <f>768.68340771397811</f>
          <cx>-10.291821702893024</cx>
          <cy>3.7142687950142763</cy>
          <k1>0.054258424223576199</k1>
          <k2>-0.1179548245864302</k2>
          <k3>0.054258424223576199</k1>
          <k4>-0.1179548245864302</k2>
          <p1>-0.0011294399122456702</p1>
          <p2>0.0022433983854041159</p2>
        </calibration>