Avoid slightly silly warnings from Clang

Clang (at least the one from newest Xcode 7 Beta) warn both that
fResult "is used uninitialized whenever 'if' condition is false" *and*
that the very same "condition is always true".

Change-Id: I9e2424e7323046edbfe1af3c9f960df49e0809dd

tools/source/generic/color.cxx

@@ -319,7 +319,7 @@ void Color::ApplyTintOrShade(sal_Int16 n100thPercent)
 
     basegfx::BColor aBColor = basegfx::tools::rgb2hsl(getBColor());
     double fFactor = 1.0 - (std::abs(double(n100thPercent)) / 10000.0);
-    double fResult;
+    double fResult = 0;
 
     if (n100thPercent > 0) // tint
     {