diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
new file mode 100644
index 0000000..fb4cd16
--- /dev/null
+++ b/.devcontainer/devcontainer.json
@@ -0,0 +1,5 @@
+{
+  "tasks": {
+    "test": "npm install && npm test"
+  }
+}
\ No newline at end of file
diff --git a/src/sportlink-to-mailchimp-converter.ts b/src/sportlink-to-mailchimp-converter.ts
index e703447..59bd7ec 100644
--- a/src/sportlink-to-mailchimp-converter.ts
+++ b/src/sportlink-to-mailchimp-converter.ts
@@ -76,7 +76,7 @@ const sportlinkRowToContact = (row: SportlinkRow, config: SportlinkToMailchimpCo
   }
 
   // If not tagged yet, assume Athletics
-  if (tags.length === 0) {
+  if (tags.length === 0 && categorie !== null && categorie !== undefined) {
     tags.push(`Atletiek ${stripGender(categorie)}`)
   }
 
@@ -141,4 +141,4 @@ const parseCsv = async (file: LocalFile) => new Promise<SportlinkRow[]>((resolve
 
 const formatParseErrors = (errors: ParseError[]): string => errors
   .map(error => `type: ${error.type}, code: ${error.code}, message: ${error.message}, row: ${error.row}, index: ${error.index}`)
-  .join('\n')
\ No newline at end of file
+  .join('\n')
diff --git a/src/string-utilities.test.ts b/src/string-utilities.test.ts
index 915f28f..3a75f7c 100644
--- a/src/string-utilities.test.ts
+++ b/src/string-utilities.test.ts
@@ -1,37 +1,42 @@
-import { stripGender, isNullOrEmpty, trimSpacesAndRemoveDoubleQuotes } from './string-utilities'
-
-describe('stripGender', () => {
-  it('should remove gender-related words and trim the string', () => {
-    expect(stripGender('Meisjes kleding')).toBe('kleding')
-    expect(stripGender('Jongens schoenen')).toBe('schoenen')
-    expect(stripGender('Vrouwen accessoires')).toBe('accessoires')
-    expect(stripGender('Mannen horloges')).toBe('horloges')
-    expect(stripGender('Unisex kleding')).toBe('Unisex kleding') // No gender-related word
-  })
-})
-
-describe('isNullOrEmpty', () => {
-  it('should return true for undefined, null, or empty strings', () => {
-    expect(isNullOrEmpty(undefined!)).toBe(true)
-    expect(isNullOrEmpty(null!)).toBe(true)
-    expect(isNullOrEmpty('')).toBe(true)
-  })
-
-  it('should return false for non-empty strings', () => {
-    expect(isNullOrEmpty('text')).toBe(false)
-    expect(isNullOrEmpty(' ')).toBe(false)
-  })
-})
-
-describe('trimSpacesAndRemoveDoubleQuotes', () => {
-  it('should trim spaces and remove double quotes', () => {
-    expect(trimSpacesAndRemoveDoubleQuotes(' "text" ')).toBe('text')
-    expect(trimSpacesAndRemoveDoubleQuotes(' "text')).toBe('text')
-    expect(trimSpacesAndRemoveDoubleQuotes('text" ')).toBe('text')
-    expect(trimSpacesAndRemoveDoubleQuotes('text')).toBe('text')
-  })
-
-  it('should handle empty strings', () => {
-    expect(trimSpacesAndRemoveDoubleQuotes('')).toBe('')
-  })
-})
+import { stripGender, isNullOrEmpty, trimSpacesAndRemoveDoubleQuotes } from './string-utilities'
+
+describe('stripGender', () => {
+  it('should remove gender-related words and trim the string', () => {
+    expect(stripGender('Meisjes kleding')).toBe('kleding')
+    expect(stripGender('Jongens schoenen')).toBe('schoenen')
+    expect(stripGender('Vrouwen accessoires')).toBe('accessoires')
+    expect(stripGender('Mannen horloges')).toBe('horloges')
+    expect(stripGender('Unisex kleding')).toBe('Unisex kleding') // No gender-related word
+  })
+
+  it('should return an empty string for null or undefined values', () => {
+    expect(stripGender(null!)).toBe('')
+    expect(stripGender(undefined!)).toBe('')
+  })
+})
+
+describe('isNullOrEmpty', () => {
+  it('should return true for undefined, null, or empty strings', () => {
+    expect(isNullOrEmpty(undefined!)).toBe(true)
+    expect(isNullOrEmpty(null!)).toBe(true)
+    expect(isNullOrEmpty('')).toBe(true)
+  })
+
+  it('should return false for non-empty strings', () => {
+    expect(isNullOrEmpty('text')).toBe(false)
+    expect(isNullOrEmpty(' ')).toBe(false)
+  })
+})
+
+describe('trimSpacesAndRemoveDoubleQuotes', () => {
+  it('should trim spaces and remove double quotes', () => {
+    expect(trimSpacesAndRemoveDoubleQuotes(' "text" ')).toBe('text')
+    expect(trimSpacesAndRemoveDoubleQuotes(' "text')).toBe('text')
+    expect(trimSpacesAndRemoveDoubleQuotes('text" ')).toBe('text')
+    expect(trimSpacesAndRemoveDoubleQuotes('text')).toBe('text')
+  })
+
+  it('should handle empty strings', () => {
+    expect(trimSpacesAndRemoveDoubleQuotes('')).toBe('')
+  })
+})
diff --git a/src/string-utilities.ts b/src/string-utilities.ts
index ebbaecf..3617c0a 100644
--- a/src/string-utilities.ts
+++ b/src/string-utilities.ts
@@ -1,5 +1,10 @@
-const regexGender = /Meisjes|Jongens|Vrouwen|Mannen/
-export const stripGender = (categorie: string) => categorie.replace(regexGender, '').trim()
-
-export const isNullOrEmpty = (text: string) => text === undefined || text === null || text.length <= 0
-export const trimSpacesAndRemoveDoubleQuotes = (text: string) => text.trim().split('"').join('')
+const regexGender = /Meisjes|Jongens|Vrouwen|Mannen/
+export const stripGender = (categorie: string) => {
+  if (categorie === null || categorie === undefined) {
+    return ''
+  }
+  return categorie.replace(regexGender, '').trim()
+}
+
+export const isNullOrEmpty = (text: string) => text === undefined || text === null || text.length <= 0
+export const trimSpacesAndRemoveDoubleQuotes = (text: string) => text.trim().split('"').join('')