[NFC] Remove dead branch.

The variable `storage` was defined as `nullptr` a couple lines above and
then is check for null, a spurious check.  Eliminate that
nullcheck--it's always true.

Author: nate-chandler

lib/SILGen/SILGenType.cpp

@@ -423,24 +423,22 @@ template<typename T> class SILGenWitnessTable : public SILWitnessVisitor<T> {
 
     // If it's not an accessor, just look for the witness.
     if (!reqAccessor) {
-      if (!storage) {
-        if (auto witness = asDerived().getWitness(reqDecl)) {
-          auto newDecl = requirementRef.withDecl(witness.getDecl());
-          // Only import C++ methods as foreign. If the following
-          // Objective-C function is imported as foreign:
-          //   () -> String
-          // It will be imported as the following type:
-          //   () -> NSString
-          // But the first is correct, so make sure we don't mark this witness
-          // as foreign.
-          if (dyn_cast_or_null<clang::CXXMethodDecl>(
-                  witness.getDecl()->getClangDecl()))
-            newDecl = newDecl.asForeign();
-          return addMethodImplementation(
-              requirementRef, getWitnessRef(newDecl, witness), witness);
-        }
-        return asDerived().addMissingMethod(requirementRef);
-      } // else, fallthrough to the usual accessor handling!
+      if (auto witness = asDerived().getWitness(reqDecl)) {
+        auto newDecl = requirementRef.withDecl(witness.getDecl());
+        // Only import C++ methods as foreign. If the following
+        // Objective-C function is imported as foreign:
+        //   () -> String
+        // It will be imported as the following type:
+        //   () -> NSString
+        // But the first is correct, so make sure we don't mark this witness
+        // as foreign.
+        if (dyn_cast_or_null<clang::CXXMethodDecl>(
+                witness.getDecl()->getClangDecl()))
+          newDecl = newDecl.asForeign();
+        return addMethodImplementation(
+            requirementRef, getWitnessRef(newDecl, witness), witness);
+      }
+      return asDerived().addMissingMethod(requirementRef);
     } else {
       // Otherwise, we need to map the storage declaration and then get
       // the appropriate accessor for it.