Reduce indentation by returning early on error condition

Change-Id: Iebf6eca68f0dcba87ab517952009ee6dfb4b588c
Reviewed-on: https://gerrit.libreoffice.org/54475Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>

sfx2/source/doc/docfile.cxx

@@ -3667,9 +3667,12 @@ bool SfxMedium::SignContents_Impl(const Reference<XCertificate> xCert, const OUS
 {
     bool bChanges = false;
 
-    // the medium should be closed to be able to sign, the caller is responsible to close it
-    if ( !IsOpen() && !GetError() )
+    if (IsOpen() || GetError())
     {
+        SAL_WARN("sfx.doc", "The medium must be closed by the signer!");
+        return bChanges;
+    }
+
     // The component should know if there was a valid document signature, since
     // it should show a warning in this case
     uno::Reference< security::XDocumentDigitalSignatures > xSigner(
@@ -3842,7 +3845,6 @@ bool SfxMedium::SignContents_Impl(const Reference<XCertificate> xCert, const OUS
     }
 
     ResetError();
-    }
 
     return bChanges;
 }