Return early if the `/crds` directory does not exist.

Don't silently discard the error from `os.Stat`.

Signed-off-by: Zach Burgess <zachburg@google.com>

pkg/cmd/testdata/output/lint-chart-with-bad-subcharts-with-subcharts.txt

@@ -3,7 +3,6 @@
 [ERROR] templates/: error unpacking subchart bad-subchart in chart-with-bad-subcharts: validation: chart.metadata.name is required
 [ERROR] : unable to load chart
 	error unpacking subchart bad-subchart in chart-with-bad-subcharts: validation: chart.metadata.name is required
-[ERROR] crds/: error unpacking subchart bad-subchart in chart-with-bad-subcharts: validation: chart.metadata.name is required
 
 ==> Linting testdata/testcharts/chart-with-bad-subcharts/charts/bad-subchart
 [ERROR] Chart.yaml: name is required
@@ -13,7 +12,6 @@
 [ERROR] templates/: validation: chart.metadata.name is required
 [ERROR] : unable to load chart
 	validation: chart.metadata.name is required
-[ERROR] crds/: validation: chart.metadata.name is required
 
 ==> Linting testdata/testcharts/chart-with-bad-subcharts/charts/good-subchart
 [INFO] Chart.yaml: icon is recommended

pkg/cmd/testdata/output/lint-chart-with-bad-subcharts.txt

@@ -3,6 +3,5 @@
 [ERROR] templates/: error unpacking subchart bad-subchart in chart-with-bad-subcharts: validation: chart.metadata.name is required
 [ERROR] : unable to load chart
 	error unpacking subchart bad-subchart in chart-with-bad-subcharts: validation: chart.metadata.name is required
-[ERROR] crds/: error unpacking subchart bad-subchart in chart-with-bad-subcharts: validation: chart.metadata.name is required
 
 Error: 1 chart(s) linted, 1 chart(s) failed

pkg/cmd/testdata/output/lint-quiet-with-error.txt

@@ -4,6 +4,5 @@
 [ERROR] templates/: cannot load Chart.yaml: error converting YAML to JSON: yaml: line 6: did not find expected '-' indicator
 [ERROR] : unable to load chart
 	cannot load Chart.yaml: error converting YAML to JSON: yaml: line 6: did not find expected '-' indicator
-[ERROR] crds/: cannot load Chart.yaml: error converting YAML to JSON: yaml: line 6: did not find expected '-' indicator
 
 Error: 2 chart(s) linted, 1 chart(s) failed