Fix the NPE issue in provisioner resource/datasource

[ramya-bangera]

1. What this PR does / why we need it:
   Added the fix to return without trying to parse the nil response in case of any error.

2. Which issue(s) this PR fixes
   Internal Jira

3. Additional information

4. Special notes for your reviewer

<testsuite name="github.com/vmware/terraform-provider-tanzu-mission-control/internal/resources/provisioner" tests="2" failures="0" errors="0" id="230" hostname="sc2-10-187-102-46.nimbus.eng.vmware.com" time="45.050" timestamp="2024-01-19T07:26:16Z">
		<properties>
			<property name="coverage.statements.pct" value="62.80"></property>
		</properties>
		<testcase name="TestAcceptanceForProvisionerDataSource" classname="github.com/vmware/terraform-provider-tanzu-mission-control/internal/resources/provisioner" time="15.960">
			<system-out><![CDATA[    provisioner_data_source_test.go:43: provisioner datasource acceptance test complete!]]></system-out>
		</testcase>
		<testcase name="TestAcceptanceForProvisionerResource" classname="github.com/vmware/terraform-provider-tanzu-mission-control/internal/resources/provisioner" time="29.080">
			<system-out><![CDATA[    provisioner_resource_test.go:86: provisioner resource acceptance test complete!]]></system-out>
		</testcase>
	</testsuite>

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (ee9e28b) 25.31% compared to head (25c9eca) 25.29%.

Files	Patch %	Lines
...l/resources/provisioner/data_source_provisioner.go	0.00%	2 Missing ⚠️
...rnal/resources/provisioner/resource_provisioner.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #373      +/-   ##
==========================================
- Coverage   25.31%   25.29%   -0.03%     
==========================================
  Files         192      192              
  Lines       16665    16668       +3     
==========================================
- Hits         4219     4216       -3     
- Misses      12229    12234       +5     
- Partials      217      218       +1     

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The merge-base changed after approval.

[github-actions]

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