Some kernels have frandom and erandom

When a users kernel has frandom and erandom this would cause the whole app to crash.

When using erandom the system doesn't use any entropy at all.

src/com/fsck/k9/PRNGFixes.java

@@ -215,8 +215,7 @@ public final class PRNGFixes {
                 out.flush();
                 mSeeded = true;
             } catch (IOException e) {
-                throw new SecurityException(
-                        "Failed to mix seed into " + URANDOM_FILE, e);
+                mSeeded = true;
             }
         }