Do not assign negative values to unsigned variables

apps/openmw/mwrender/renderingmanager.cpp

@@ -860,8 +860,7 @@ namespace MWRender
     {
         RenderingManager::RayResult result;
         result.mHit = false;
-        result.mHitRefnum.mContentFile = -1;
-        result.mHitRefnum.mIndex = -1;
+        result.mHitRefnum.unset();
         result.mRatio = 0;
         if (intersector->containsIntersections())
         {

components/nifosg/nifloader.cpp

@@ -238,7 +238,7 @@ namespace NifOsg
         std::string mFilename;
         unsigned int mVersion, mUserVersion, mBethVersion;
 
-        size_t mFirstRootTextureIndex = -1;
+        size_t mFirstRootTextureIndex{~0u};
         bool mFoundFirstRootTexturingProperty = false;
 
         bool mHasNightDayLabel = false;

components/sceneutil/lightmanager.cpp

@@ -132,7 +132,7 @@ namespace SceneUtil
             if (value[0] < 0)
             {
                 positiveColor *= -1.0;
-                signBit = -1;
+                signBit = ~0u;
             }
             unsigned int packedColor = asRGBA(positiveColor);
             std::memcpy(&(*mData)[getOffset(index, Diffuse)], &packedColor, sizeof(unsigned int));