[SE-0258] Check for a NULL type.

Within invalid code, we might encounter expressions without type
information yet. Check for NULL here.

Fixes crash from rdar://problem/53120878.

Author: DougGregor

lib/AST/Decl.cpp

@@ -5838,7 +5838,8 @@ Expr *swift::findOriginalPropertyWrapperInitialValue(VarDecl *var,
 
         // ... producing a value of the same nominal type as the innermost
         // property wrapper.
-        if (call->getType()->getAnyNominal() != innermostNominal)
+        if (!call->getType() ||
+            call->getType()->getAnyNominal() != innermostNominal)
           return { true, E };
 
         // Find the implicit initialValue argument.

validation-test/compiler_crashers_2_fixed/0201-rdar53120878.swift

@@ -0,0 +1,4 @@
+// RUN: not %target-swift-frontend -typecheck %s
+public struct Use { @Wrap var value: some Doubl = 1.0 }
+@propertyWrapper public struct Wrap { public var wrappedValue: Double }
+