FitParameterItem: simplify P_MIN

GUI/Model/Job/FitParameterItem.cpp

@@ -55,7 +55,7 @@ FitParameterItem::FitParameterItem()
     setDefaultTag(T_LINK);
 
     startValueItem()->setLimits(RealLimits::limitless());
-    getItem(P_MIN)->setLimits(RealLimits::limitless());
+    minimumItem()->setLimits(RealLimits::limitless());
     getItem(P_MAX)->setLimits(RealLimits::limitless());
 
     onTypeChange();
@@ -82,8 +82,8 @@ void FitParameterItem::initMinMaxValues(const RealLimits& limits)
     if (limits.hasUpperLimit() && max > limits.upperLimit())
         max = limits.upperLimit();
 
-    setItemValue(P_MIN, min);
-    getItem(P_MIN)->setLimits(limits);
+    setMinimum(min);
+    minimumItem()->setLimits(limits);
     setItemValue(P_MAX, max);
     getItem(P_MAX)->setLimits(limits);