Check for available lab profile

While falling back to lab jzczhz blending we should check if
- a profile is provided
- a file profile is available
- the corresponding input profile could be created.

If not, we can't do anything here and just leave out blending.

Author: jenshannoschwalm

src/develop/blends/blendif_rgb_jzczhz.c

@@ -240,15 +240,21 @@ static void _blendif_combine_channels(const float *const restrict pixels,
     if(dt_is_valid_colormatrix(profile->matrix_out_transposed[0][0]))
       _blendif_jzczhz(pixels, mask, stride, parameters + DEVELOP_BLENDIF_PARAMETER_ITEMS * DEVELOP_BLENDIF_Jz_in,
                     invert_mask, profile);
-    else
+    else if(profile)
     {
-      cmsHPROFILE *input = dt_colorspaces_get_profile(profile->type, profile->filename, DT_PROFILE_DIRECTION_IN)->profile;
+      const gboolean test = (profile->type != DT_COLORSPACE_FILE)
+                        || (profile->type == DT_COLORSPACE_FILE && dt_util_test_image_file(profile->filename));
+
+      cmsHPROFILE *input = test ? dt_colorspaces_get_profile(profile->type, profile->filename, DT_PROFILE_DIRECTION_IN)->profile : NULL;
       cmsHPROFILE *Lab = dt_colorspaces_get_profile(DT_COLORSPACE_LAB, "", DT_PROFILE_DIRECTION_ANY)->profile;
-      cmsHTRANSFORM *xform = cmsCreateTransform(input, TYPE_RGBA_FLT, Lab, TYPE_LabA_FLT, profile->intent, 0);
+      cmsHTRANSFORM *xform = input ? cmsCreateTransform(input, TYPE_RGBA_FLT, Lab, TYPE_LabA_FLT, profile->intent, 0) : NULL;
 
-      _blendif_jzczhz_lab(pixels, mask, stride, parameters + DEVELOP_BLENDIF_PARAMETER_ITEMS * DEVELOP_BLENDIF_Jz_in,
+      if(xform)
+      {
+        _blendif_jzczhz_lab(pixels, mask, stride, parameters + DEVELOP_BLENDIF_PARAMETER_ITEMS * DEVELOP_BLENDIF_Jz_in,
                     invert_mask, xform);
-      cmsDeleteTransform(xform);
+        cmsDeleteTransform(xform);
+      }
     }
   }
 }