SvgSerializer: Fix error message logic

If we have no storeys *and* we didn't find any suitable fall-back, then
the error message makes sense.

src/ifcconvert/SvgSerializer.cpp

@@ -390,7 +390,7 @@ void SvgSerializer::setFile(IfcParse::IfcFile* f) {
 				}
 			}
 		}
-	}
 
-	Logger::Error("No building storeys encountered, output might be invalid or missing");
-}
+		Logger::Error("No building storeys encountered, output might be invalid or missing");
+	}
+}