Fix exception when rotating when counter are used, by prevent negativ…

…e fontsize (greenshot#382)

src/Greenshot.Editor/Drawing/StepLabelContainer.cs

@@ -204,7 +204,7 @@ public override void Draw(Graphics graphics, RenderMode rm)
                 EllipseContainer.DrawEllipse(rect, graphics, rm, 0, Color.Transparent, fillColor, false);
             }
 
-            float fontSize = Math.Min(Width, Height) / 1.4f;
+            float fontSize = Math.Min(Math.Abs(Width), Math.Abs(Height)) / 1.4f;
             using FontFamily fam = new FontFamily(FontFamily.GenericSansSerif.Name);
             using Font font = new Font(fam, fontSize, FontStyle.Bold, GraphicsUnit.Pixel);
             TextContainer.DrawText(graphics, rect, 0, lineColor, false, _stringFormat, text, font);