fix zoom crash when wheel on square charts

NanoVNASaver/Charts/Chart.py

@@ -103,6 +103,11 @@ class Chart(QtWidgets.QWidget):
         self.name = name
         self.sweepTitle = ''
 
+        self.leftMargin = 30
+        self.rightMargin = 20
+        self.bottomMargin = 20
+        self.topMargin = 30
+
         self.dim = ChartDimensions()
         self.dragbox = ChartDragBox()
         self.flag = ChartFlags()

NanoVNASaver/Charts/Polar.py

@@ -52,6 +52,3 @@ class PolarChart(SquareChart):
                     center_x - width_45, center_y + height_45)
 
         self.drawTitle(qp)
-
-    def zoomTo(self, x1, y1, x2, y2):
-        raise NotImplementedError()

NanoVNASaver/Charts/Smith.py

@@ -94,6 +94,3 @@ class SmithChart(SquareChart):
             qp.drawText(
                 QtCore.QRect(centerX - 50, centerY - 4 + r, 100, 20),
                 QtCore.Qt.AlignCenter, str(swr))
-
-    def zoomTo(self, x1, y1, x2, y2):
-        raise NotImplementedError()

NanoVNASaver/Charts/Square.py

@@ -138,8 +138,12 @@ class SquareChart(Chart):
             m.setFrequency(str(round(target[minimum_position].freq)))
             m.frequencyInput.setText(str(round(target[minimum_position].freq)))
 
+
     def getXPosition(self, d: Datapoint) -> int:
         return int(self.width()/2 + d.re * self.dim.width/2)
 
     def getYPosition(self, d: Datapoint) -> int:
         return int(self.height()/2 + d.im * -1 * self.dim.height/2)
+
+    def zoomTo(self, x1, y1, x2, y2):
+        pass

NanoVNASaver/Charts/TDR.py

@@ -41,10 +41,10 @@ class TDRChart(Chart):
     def __init__(self, name):
         super().__init__(name)
         self.tdrWindow = None
-        self.leftMargin = 30
-        self.rightMargin = 20
+
         self.bottomMargin = 25
         self.topMargin = 20
+
         self.setMinimumSize(300, 300)
         self.setSizePolicy(
             QtWidgets.QSizePolicy(