ExtBasic.c: oppdir, The right operand of '==' is a garbage value

BD_xxxxx are a bitmask.  So it makes sense due to equality check to
set to zero so it becomes a no-op situation.

I assume lb->dir not matching one of the 4 BD_xxxxx labels would be
a data error anyway and should never occur.

SonarCloud
The right operand of '==' is a garbage value
https://sonarcloud.io/project/issues?open=AZJB16p0NGfDNup0RiW9&id=dlmiles_magic

extract/ExtBasic.c

@@ -1267,6 +1267,8 @@ extComputeEffectiveLW(rlengthptr, rwidthptr, numregions, chop)
 	    case BD_RIGHT:  oppdir = BD_LEFT;   break;
 	    case BD_TOP:    oppdir = BD_BOTTOM; break;
 	    case BD_BOTTOM: oppdir = BD_TOP;    break;
+	    default:        ASSERT(FALSE, "oppdir"); /* should never happen */
+	                    oppdir = 0;         break;
 	}
 
 	/* First pass: Find the distance of the closest segment within	*/