Revert "Fix NPE in SourceFileRewriter: code could be removed entirely."

This reverts commit 03af4092b5f4e4ade2a0b846cc7d42df6bdaeafd.

Reason for revert:
Its predecessor will be reverted, so this should be reverted ahead.

Change-Id: I1a709ff6e39075db0e0e7db1826bcc525ecd77fc
diff --git a/src/main/java/com/android/tools/r8/naming/SourceFileRewriter.java b/src/main/java/com/android/tools/r8/naming/SourceFileRewriter.java
index 8745ca5..5ab50fc 100644
--- a/src/main/java/com/android/tools/r8/naming/SourceFileRewriter.java
+++ b/src/main/java/com/android/tools/r8/naming/SourceFileRewriter.java
@@ -48,7 +48,7 @@
         }
         Code code = encodedMethod.getCode();
         // Other kinds of {@link Code} do not have debug_info_item.
-        if (code == null || !code.isDexCode()) {
+        if (!code.isDexCode()) {
           return;
         }
         if (code.asDexCode().getDebugInfo() == null) {