utils: mdldec: smd.c: prevent division by zero.

utils/mdldec/smd.c

@@ -439,10 +439,13 @@ static void WriteFrameInfo( FILE *fp, mstudioanim_t *anim, mstudioseqdesc_t *seq
 		CalcBonePosition( anim, bone, motion, frame );
 
 		if( bone->parent == -1 )
+		{
+			if( seqdesc->numframes > 1 && frame > 0 )
 			{
 				scale = frame / (float)( seqdesc->numframes - 1 );
 
 				VectorMA( motion, scale, seqdesc->linearmovement, motion );
+			}
 
 			ProperBoneRotationZ( motion, 270.0f );
 		}