Fix T57504: Scaling 3D cursor crashes

Referenced by issue #57504, Blender 2.80 crash while dragging cursor and start scaling
Referenced by issue #56011, Crash dragging Cursor tool and hitting S (scale)

source/blender/editors/transform/transform.c

@@ -3677,7 +3677,8 @@ static void ElementResize(TransInfo *t, TransDataContainer *tc, TransData *td, f
 		copy_v3_v3(center, tc->center_local);
 	}
 
-	if (td->ext) {
+	/* Size checked needed since the 3D cursor only uses rotation fields. */
+	if (td->ext && td->ext->size) {
 		float fsize[3];
 
 		if (t->flag & (T_OBJECT | T_TEXTURE | T_POSE)) {