Sketcher: [skip ci] Fix coverity warning

Coverity warnings fixed:

CID 129530 (#1 of 1): Uninitialized scalar field (UNINIT_CTOR)
2. uninit_member: Non-static class member pixelScalingFactor is not initialized in this constructor nor in any functions that it calls.

src/Mod/Sketcher/Gui/ViewProviderSketch.cpp

@@ -187,6 +187,7 @@ struct EditData {
     MarkerSize(7),
     coinFontSize(17), // this value is in pixels, 17 pixels
     constraintIconSize(15),
+    pixelScalingFactor(1.0),
     blockedPreselection(false),
     FullyConstrained(false),
     //ActSketch(0), // if you are wondering, it went to SketchObject, accessible via getSolvedSketch() and via SketchObject interface as appropriate