Fixed MikktSpaceTangentGenerator that was not replacing existing Tangent buffers on the mesh. That could cause crashes when the old tangent buffer did not have the same amount of components

jme3-core/src/main/java/com/jme3/util/mikktspace/MikkTSpaceImpl.java

@@ -21,15 +21,12 @@ public class MikkTSpaceImpl implements MikkTSpaceContext {
 
     public MikkTSpaceImpl(Mesh mesh) {
         this.mesh = mesh;
-        VertexBuffer tangentBuffer = mesh.getBuffer(VertexBuffer.Type.Tangent);
+        //replacing any existing tangent buffer, if you came here you want them new.
-        if(tangentBuffer == null){
+        mesh.clearBuffer(VertexBuffer.Type.Tangent);
         FloatBuffer fb = BufferUtils.createFloatBuffer(mesh.getVertexCount() * 4);
         mesh.setBuffer(VertexBuffer.Type.Tangent, 4, fb);
     }
 
-        //TODO ensure the Tangent buffer exists, else create one.
-    }
-
     @Override
     public int getNumFaces() {
         return mesh.getTriangleCount();