Error "No stream named styles.xml found." when reading ODS file

Error message when opening an ODS-file:

No stream named styles.xml found.

The ods file was created by a data export tool and only contained the following files:

• mimetype
• content.xml
• meta.xml
• META-INF/manifest.xml

An OpenDocument package is not required to contain a styles.xml file:

OpenDocument Version 1.2
Part 1: OpenDocument Schema
section 2.2.1 A.2)
"contain at least **one** of the following files : content.xml and styles.xml"

The current code already supports reading without styles.xml [plugins/openoffice/openoffice-read.c:13904] except for the check at [plugins/openoffice/openoffice-read.c:13741].

See attached patch gnumeric-ods-no-style_xml.patch for a fix.