Fail fast on extended tetrahedral perception, there were some other changes here that I've just removed since they don't make sense.

johnmay · johnmay · commit 2591f993d996 · 2021-01-17T21:36:03.000Z
diff --git a/base/standard/src/main/java/org/openscience/cdk/stereo/StereoElementFactory.java b/base/standard/src/main/java/org/openscience/cdk/stereo/StereoElementFactory.java
@@ -795,6 +795,7 @@ ExtendedTetrahedral createExtendedTetrahedral(int v, Stereocenters stereocenters
                 if (w == v) continue;
                 if (bond.getOrder() != IBond.Order.SINGLE) continue;
                 if (isUnspecified(bond)) return null;
+                if (n == 2) return null;
                 neighbors[n] = container.getAtom(w);
                 elevation[n] = elevationOf(terminals[0], bond);
                 n++;
@@ -806,6 +807,7 @@ ExtendedTetrahedral createExtendedTetrahedral(int v, Stereocenters stereocenters
                 IBond bond = bondMap.get(t1, w);
                 if (bond.getOrder() != IBond.Order.SINGLE) continue;
                 if (isUnspecified(bond)) return null;
+                if (n == 4) return null;
                 neighbors[n] = container.getAtom(w);
                 elevation[n] = elevationOf(terminals[1], bond);
                 n++;
@@ -1208,6 +1210,9 @@ ExtendedTetrahedral createExtendedTetrahedral(int v, Stereocenters stereocenters
             IAtom focus = container.getAtom(v);
 
             if (hasUnspecifiedParity(focus)) return null;
+            
+            if (container.getConnectedBondsCount(focus) != 2)
+        	    return null;
 
             IAtom[] terminals = ExtendedTetrahedral.findTerminalAtoms(container, focus);
             IAtom[] neighbors = new IAtom[4];
