fix: check config file before accessing values (runfinch#1120)

Signed-off-by: Sam Chew <stchew@amazon.com>

Author: chews93319

cmd/finch/main.go

@@ -45,7 +45,7 @@ func initializeNerdctlCommands(
 		allNerdctlCommands = append(allNerdctlCommands, nerdctlCommandCreator.create(cmdName, cmdDescription))
 	}
 
-	if fc.DockerCompat {
+	if fc != nil && fc.DockerCompat {
 		for cmdName, cmdDescription := range dockerCompatCmds {
 			allNerdctlCommands = append(allNerdctlCommands, nerdctlCommandCreator.create(cmdName, cmdDescription))
 		}

cmd/finch/nerdctl.go

@@ -249,7 +249,7 @@ var cmdFlagSetMap = map[string]map[string]sets.Set[string]{
 
 // converts "docker build --load" flag to "nerdctl build --output=type=docker".
 func handleDockerBuildLoad(_ NerdctlCommandSystemDeps, fc *config.Finch, nerdctlCmdArgs []string, index int) error {
-	if fc.DockerCompat {
+	if fc != nil && fc.DockerCompat {
 		nerdctlCmdArgs[index] = "--output=type=docker"
 	}
 
@@ -280,7 +280,7 @@ func handleBuildx(_ NerdctlCommandSystemDeps, fc *config.Finch, cmdName *string,
 }
 
 func handleDockerCompatInspect(_ NerdctlCommandSystemDeps, fc *config.Finch, cmdName *string, args *[]string) error {
-	if !fc.DockerCompat {
+	if fc == nil || !fc.DockerCompat {
 		return nil
 	}