Fixed crash

app/build.gradle

@@ -12,8 +12,8 @@ android {
         applicationId "eu.faircode.email"
         minSdkVersion 21
         targetSdkVersion 30
-        versionCode 1343
-        versionName "1.1343"
+        versionCode 1344
+        versionName "1.1344"
         archivesBaseName = "FairEmail-v$versionName"
 
         // https://en.wikipedia.org/wiki/List_of_dinosaur_genera

app/src/main/java/eu/faircode/email/FragmentCompose.java

@@ -4507,16 +4507,24 @@ public class FragmentCompose extends FragmentBase {
                                 checkAddress(acc, context);
                                 checkAddress(abcc, context);
 
-                                List<String> all = new ArrayList<>();
+                                List<InternetAddress> check = new ArrayList<>();
+                                List<String> checked = new ArrayList<>();
                                 List<String> dup = new ArrayList<>();
-                                for (InternetAddress a : Helper.concat(Helper.concat(ato, acc), abcc)) {
+                                if (ato != null)
+                                    check.addAll(Arrays.asList(ato));
+                                if (acc != null)
+                                    check.addAll(Arrays.asList(acc));
+                                if (abcc != null)
+                                    check.addAll(Arrays.asList(abcc));
+
+                                for (InternetAddress a : check) {
                                     String email = a.getAddress();
                                     if (TextUtils.isEmpty(email))
                                         continue;
-                                    if (all.contains(a.getAddress()))
+                                    if (checked.contains(a.getAddress()))
                                         dup.add(email);
                                     else
-                                        all.add(email);
+                                        checked.add(email);
                                 }
 
                                 if (dup.size() > 0)

app/src/main/java/eu/faircode/email/Helper.java

@@ -1564,17 +1564,6 @@ public class Helper {
         return result;
     }
 
-    @SuppressWarnings("unchecked")
-    public static <T> T[] concat(T[] a, T[] b) {
-        if (a == null)
-            a = (T[]) new Object[0];
-        if (b == null)
-            b = (T[]) new Object[0];
-        T[] both = Arrays.copyOf(a, a.length + b.length);
-        System.arraycopy(b, 0, both, a.length, b.length);
-        return both;
-    }
-
     static boolean equal(String[] a1, String[] a2) {
         if (a1 == null && a2 == null)
             return true;