Application breakes when the Portfolio spreadsheet has just the title lines

[CarlosOliveira1988]

Describe the bug

There are some specific cases that the application brakes such as:

1. when the Portfolio spreadsheet is filled in with just the title lines
2. when the resultant 'Renda Variável' tab has 0 or 1 line

To Reproduce

Steps to reproduce the behavior: 1.1. Go to the target Portfolio spreadsheet 1.2. Erase all lines, except the titles line 1.3. Run the application and open the target Portfolio spreadsheet 1.4. See error

2.1. Go to the target Portfolio spreadsheet 2.2. Add 'compra'/'venda' lines in a way that the opened position resultant is equal to 0 (all positions are closed) or 1 (just 1 opened position like 200 BBAS3) 2.3. Run the application and open the target Portfolio spreadsheet 2.4. See error

Expected behavior

The application shall work normally and all the mentioned exceptions shall be correctly handled.

Screenshots

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Desktop (please complete the following information):

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Additional context

N/A.

[CarlosOliveira1988]

This ticket is resolved by the commit ac06182. Please, check the results.