Support extraction out of control-flow IfInstruction even if it isn't using a Block as TrueInst/FalseInst.

ICSharpCode.Decompiler/IL/Transforms/FixLoneIsInst.cs

@@ -46,6 +46,9 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 				if (isInst.Parent.MatchCompEqualsNull(out _) || isInst.Parent.MatchCompNotEqualsNull(out _)) {
 					continue; // supported pattern "expr is T"
 				}
+				if (isInst.Parent is Block { Kind: BlockKind.ControlFlow }) {
+					continue; // supported via StatementBuilder.VisitIsInst
+				}
 				instructionsToFix.Add(isInst);
 			}
 			// Need to delay fixing until we're done with iteration, because Extract() modifies parents

ICSharpCode.Decompiler/IL/Transforms/ILExtraction.cs

@@ -97,6 +97,14 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 			ctx.FlagsBeingMoved = instToExtract.Flags;
 			ILInstruction inst = instToExtract;
 			while (inst != null) {
+				if (inst.Parent is IfInstruction ifInst && inst.SlotInfo != IfInstruction.ConditionSlot) {
+					// this context doesn't support extraction, but maybe we can create a block here?
+					if (ifInst.ResultType == StackType.Void) {
+						Block newBlock = new Block();
+						inst.ReplaceWith(newBlock);
+						newBlock.Instructions.Add(inst);
+					}
+				}
 				if (inst.Parent is Block block && block.Kind == BlockKind.ControlFlow) {
 					// We've reached the target block, and extraction is possible all the way.
 					int insertIndex = inst.ChildIndex;