Fix #114224: Bone Disappear in Pose Mode

In certain cases bones can disappear in pose mode. The cause was
that the alpha channel was not set in all cases and might use uninitialized
memory as alpha value.

Pull Request: https://projects.blender.org/blender/blender/pulls/114324

source/blender/draw/engines/overlay/overlay_armature.cc

@@ -1227,7 +1227,7 @@ static void get_pchan_color_constraint(const ThemeWireColor *bcolor,
   else if (constflag & PCHAN_HAS_CONST) {
     constraint_color = G_draw.block.color_bone_pose_constraint;
   }
-  interp_v3_v3v3(r_color, solid_color, constraint_color, 0.5f);
+  interp_v4_v4v4(r_color, solid_color, constraint_color, 0.5f);
 }
 
 /** \} */