gfx: various small fixes, better handle when a shader does not have a… #2644

Job	Run time
Template generation (score-avnd-simple-template)	19s
Template generation (score-vfx-template)	1m 17s
Template generation (score-process-template)	27s
Template generation (score-device-template)	19s
Template generation (score-offline-process-template)	17s
score-vfx-template (Windows)	8m 56s
score-process-template (Windows)	8m 30s
score-device-template (Windows)	9m 50s
score-avnd-simple-template (Windows)	7m 49s
score-offline-process-template (Windows)	7m 48s
score-vfx-template (Ubuntu)	4m 36s
score-process-template (Ubuntu)	4m 59s
score-device-template (Ubuntu)	4m 56s
score-avnd-simple-template (Ubuntu)	5m 11s
score-offline-process-template (Ubuntu)	4m 30s
score-vfx-template (macOS)	4m 54s
score-process-template (macOS)	5m 36s
score-device-template (macOS)	5m 16s
score-avnd-simple-template (macOS)	5m 6s
score-offline-process-template (macOS)	5m 12s
	1h 35m 48s

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