qstringlist array crashes program

[chrisb123]

Can someone explain this
This works

QString usage = "12.34 56.78";
 QStringList usage2 = usage.split(" ");
   foreach (QString str, usage2) { 
     qDebug() << str;    
    }

QString usage = "12.34 56.78";
 QStringList usage2 = usage.split(" ");
   foreach (QString str, usage2) { 
     qDebug() << str;    
    }

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This works

float used = usage2[0].toFloat();

float used = usage2[0].toFloat();

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This does not work

float used = usage2[1].toFloat();

float used = usage2[1].toFloat();

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