kdumpctl: check the return value of get_dump_mode_by_kernel

We should check the return value of get_dump_mode_by_kernel and exit if
there is an error.

Signed-off-by: Lichen Liu <[email protected]>

Author: licliu

kdumpctl

@@ -1687,7 +1687,9 @@ reset_crashkernel()
 					fi
 				fi
 			else
-				_dump_mode="$(get_dump_mode_by_kernel "$_kernel")"
+				if ! _dump_mode="$(get_dump_mode_by_kernel "$_kernel")"; then
+					exit 1
+				fi
 				_new_ck=$(kdump_get_arch_recommend_crashkernel "$_dump_mode")
 			fi
 		else
@@ -1726,7 +1728,9 @@ _update_crashkernel()
 	local _old_ck _new_ck
 
 	_kernel=$1
-	_dump_mode=$(get_dump_mode_by_kernel "$_kernel")
+	if ! _dump_mode=$(get_dump_mode_by_kernel "$_kernel"); then
+		exit 1
+	fi
 	_old_ck=$(get_grub_kernel_boot_parameter "$_kernel" crashkernel)
 	_kver=$(parse_kver_from_path "$_kernel")
 	# The second argument is for the case of aarch64, where installing a 64k variant on a 4k kernel, or vice versa