Have basic file check in import

Reading of files and Averaging with result of ZERO MS-Peaks should raise an error message during import.

See example:

Importing: F:\LipidXplorer-1.2.8\191105_Geko\Chol_ES_Geko\190820_Batch190627_Chol_Best\190820_39265_a.mzML

Nb. of MS scans............... 18 Nb. of MS peaks............... 215 Nb. of MS/MS scans............ 36 Nb. of MS/MS peaks............ 950 Nb. of MS peaks (after avg.).. 0 Spray stability: MaxTIC - MinTIC:............ 174.42% of median

That leads in the end to an error like this before alignment of sample:

MS filter settings............ 0.60 MS/MS filter settings......... 0.60 Avg. Nb. of MS scans.......... 18 Avg. Nb. of MS peaks.......... 25757 Avg. Nb. of MS/MS scans....... 36 Avg. Nb. of MS/MS peaks....... 7141 853.66 sec. for reading the spectra 0.00 sec. for calibrating the spectra Aligning MS spectra linear File "lx\gui\lpdxGUI.py", line 327, in run File "lx\spectraImport.py", line 588, in doImport File "lx\alignment.py", line 549, in mkSurveyLinear File "lx\spectraContainer.py", line 1044, in checkOccupation TypeError unsupported operand type(s) for *: 'float' and 'NoneType'