fix local preview green blocks with hdr on.

 table_id in cl kernel may overflow when R/G/B has
 high values.
diff --git a/cl_kernel/kernel_hdr_rgb.cl b/cl_kernel/kernel_hdr_rgb.cl
index 72729de..be12f8a 100644
--- a/cl_kernel/kernel_hdr_rgb.cl
+++ b/cl_kernel/kernel_hdr_rgb.cl
@@ -14,9 +14,9 @@
 "    int2 pos = (int2)(x, y);                                                                  "
 "    float4 pixel_in,pixel_out;									"
 "    pixel_in = read_imagef(input, sampler, pos);                             		   "
-"    pixel_out.x = convert_float(HDRTable[convert_int(pixel_in.x*1024)]/1024.0);		"
-"    pixel_out.y = convert_float(HDRTable[convert_int(pixel_in.y*1024)]/1024.0);											"
-"    pixel_out.z = convert_float(HDRTable[convert_int(pixel_in.z*1024)]/1024.0);											"
+"    pixel_out.x = convert_float(HDRTable[convert_int(pixel_in.x*1023)]/1023.0);		"
+"    pixel_out.y = convert_float(HDRTable[convert_int(pixel_in.y*1023)]/1023.0);											"
+"    pixel_out.z = convert_float(HDRTable[convert_int(pixel_in.z*1023)]/1023.0);											"
 "    pixel_out.w = 0.0;											"
 "    write_imagef(output, pos, pixel_out);                                                        "
 "}                                                                                             "