added identity check on getInverse() in CMatrix4

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@1018 dfc29bdd-3216-0410-991c-e03cc46cb475

include/matrix4.h

@@ -765,6 +765,7 @@ namespace core
 				if (j != i)
 					if (!iszero((*this)(i,j)))
 						return false;
+
 		return true;
 	}
 
@@ -1025,6 +1026,12 @@ namespace core
 		/// The inverse is calculated using Cramers rule.
 		/// If no inverse exists then 'false' is returned.
 
+		if ( this->isIdentity() )
+		{
+			out=*this;
+			return true;
+		}
+
 		const CMatrix4<T> &m = *this;
 
 		f32 d = (m(0, 0) * m(1, 1) - m(0, 1) * m(1, 0)) * (m(2, 2) * m(3, 3) - m(2, 3) * m(3, 2)) -