fix: report info-flag should not error when app undeployed

Several plugin `:report` subcommands erroneously failed with `not deployed` when an info-flag matched a property that was empty. Empty values are legitimate for configuration properties pre-deploy and the `--format json` path already returns them without error. Remove the `value_exists` check across nginx, checks, git, certs, scheduler-docker-local, and the builder-* plugins so the info-flag form behaves consistently with the JSON form.

tests/unit/builder-railpack.bats

@@ -25,6 +25,30 @@ teardown() {
   global_teardown
 }
 
+@test "(builder-railpack:report) info-flag works before deploy" {
+  run /bin/bash -c "dokku builder-railpack:report $TEST_APP --builder-railpack-railpackjson-path"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku builder-railpack:set $TEST_APP railpackjson-path railpack.alt.json"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku builder-railpack:report $TEST_APP --builder-railpack-railpackjson-path"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+  assert_output "railpack.alt.json"
+
+  run /bin/bash -c "dokku builder-railpack:report $TEST_APP --builder-railpack-invalid-flag"
+  echo "output: $output"
+  echo "status: $status"
+  assert_failure
+  assert_output_contains "Invalid flag passed"
+}
+
 @test "(builder-railpack:report) --global --builder-railpack-global-railpackjson-path" {
   run /bin/bash -c "dokku builder-railpack:set --global railpackjson-path railpack.alt.json"
   echo "output: $output"