cleaned up BasePlot._get_fluid_data code
cleaned up BasePlot._get_fluid_data code

CoolProp/CoolProp-museum,ibell/coolprop,ibell/coolprop,ibell/coolprop,CoolProp/CoolProp-museum,ibell/coolprop,CoolProp/CoolProp-museum,CoolProp/CoolProp-museum,ibell/coolprop,CoolProp/CoolProp-museum,ibell/coolprop,CoolProp/CoolProp-museum,ibell/coolprop,ibell/coolprop,CoolProp/CoolProp-museum