Bug in TTS automatic

[vbdr]

• Open TTS app
• Open example two data files of different MW and different temperature, e.g., PI_LINEAR/osc/14k-02_-10C_FS_PP_-10.osc and 4k-02_-45C_FS_PP_10.osc
• Open TTS automatic and obtain the error below

Error Traceback:
   File "/Users/victorbdr/Desktop/original_reptate2/RepTate/gui/QDataSet.py", line 1041, in handle_actionNew_Theory
    self.new_theory(th_name)
  File "/Users/victorbdr/Desktop/original_reptate2/RepTate/gui/QDataSet.py", line 1051, in new_theory
    newth = self.do_new(th_name, calculate)
  File "/Users/victorbdr/Desktop/original_reptate2/RepTate/core/DataSet.py", line 1258, in do_new
    th_id, self, self.parent_application.axarr
  File "/Users/victorbdr/Desktop/original_reptate2/RepTate/theories/TheoryTTS_Automatic.py", line 73, in __new__
    if (CmdBase.mode == CmdMode.GUI)
  File "/Users/victorbdr/Desktop/original_reptate2/RepTate/theories/TheoryTTS_Automatic.py", line 605, in __init__
    self.populate_TempComboBox()
  File "/Users/victorbdr/Desktop/original_reptate2/RepTate/theories/TheoryTTS_Automatic.py", line 675, in populate_TempComboBox
    self.set_param_value("T", float(self.cbTemp.currentText()))
ValueError: could not convert string to float: 

[jorge-ramirez-upm]

Changed code so that the ComboBox for the shift T is left empty if the loaded samples do not share any value of T