prevent multiple GPU-usage-warnings per call

functions/phaseRetrieval/holographic/phaserec_nonlinTikhonov.m

@@ -195,9 +195,10 @@ N = size(holograms(:,:,1));
 % ----------------------------------------------------------------------------------------------- %
 
 settingsCTF = settings;
-settingsCTF.optimization = struct;
 settingsCTF.padx = 0;            % Holograms are already padded,
 settingsCTF.pady = 0;            % so no more padding necessary
+settingsCTF.useGPUIfPossible = useGPU;
+settingsCTF.optimization = struct;
 initialGuess = gpuArrayIf(phaserec_ctf(holograms, fresnelNumbers, settingsCTF), useGPU);
 
 % Preliminary nonlinearity-correction in the reconstructed absorption, applied in the low-frequency