Fixed Android 7.0- compatibility

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

@@ -2837,12 +2837,16 @@ public class Helper {
     }
 
     static void secureDelete(File file) {
-        if (file.exists()) {
+        try {
-            try {
+            if (file.exists()) {
-                Files.delete(Paths.get(file.getAbsolutePath()));
+                if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) {
-            } catch (IOException ex) {
+                    if (!file.delete())
-                Log.e(ex);
+                        throw new FileNotFoundException(file.getAbsolutePath());
+                } else
+                    Files.delete(Paths.get(file.getAbsolutePath()));
             }
+        } catch (IOException ex) {
+            Log.e(ex);
         }
     }