Fix: goheader linter can throw nil pointer exception in case of a source file has not issues (#1209)

* fix potential nil pointer exception

Signed-off-by: denis-tingajkin <denis.tingajkin@xored.com>

* add test to cover

Signed-off-by: denis-tingajkin <denis.tingajkin@xored.com>

Author: denis-tingaikin

pkg/golinters/goheader.go

@@ -51,6 +51,9 @@ func NewGoHeader() *goanalysis.Linter {
 			var res []goanalysis.Issue
 			for _, file := range pass.Files {
 				i := a.Analyze(file)
+				if i == nil {
+					continue
+				}
 				issue := result.Issue{
 					Pos: token.Position{
 						Line:     i.Location().Line + 1,

test/linters_test.go

@@ -193,6 +193,9 @@ func extractRunContextFromComments(t *testing.T, sourcePath string) *runContext
 			skipMultilineComment(scanner)
 			continue
 		}
+		if strings.TrimSpace(line) == "" {
+			continue
+		}
 		if !strings.HasPrefix(line, "//") {
 			return rc
 		}

test/testdata/go-header.go renamed to test/testdata/go-header_bad.go

@@ -1,4 +1,5 @@
 /*MY TITLE!*/ // ERROR "Expected:TITLE., Actual: TITLE!"
+
 //args: -Egoheader
 //config_path: testdata/configs/go-header.yml
 package testdata

test/testdata/go-header_good.go

@@ -0,0 +1,5 @@
+/*MY TITLE.*/
+
+//args: -Egoheader
+//config_path: testdata/configs/go-header.yml
+package testdata