[cppcheck-fix] Uninitialized variable
[cppcheck-fix] Uninitialized variable

Fix issue reported by cppcheck-1.57 :
[src/Xw/Xw_ColorMap.cxx:320]: (error) Uninitialized variable: MaxUserColor

BenoitPerrot/oce,finetjul/oce,tpaviot/oce,EvgeneOskin/oce,Tech-XCorp/oce,BenoitPerrot/oce,heartvalve/oce,Tech-XCorp/oce,mathstuf/oce,heartvalve/oce,heartvalve/oce,Tridify/oce,finetjul/oce,BenoitPerrot/oce,tpaviot/oce,Tech-XCorp/oce,EvgeneOskin/oce,finetjul/oce,finetjul/oce,Tridify/oce,Tech-XCorp/oce,EvgeneOskin/oce,heartvalve/oce,EvgeneOskin/oce,mathstuf/oce,tpaviot/oce,tpaviot/oce,BenoitPerrot/oce,EvgeneOskin/oce,finetjul/oce,mathstuf/oce,Tridify/oce,Tech-XCorp/oce,mathstuf/oce,BenoitPerrot/oce,Tridify/oce,heartvalve/oce,mathstuf/oce,Tridify/oce,tpaviot/oce