Fix Null Pointer Exception in blaze caused by fdoContext being null with
Propeller.

fdoContext is a nullptr and it is not explicitly checked which causes the
NullPointerException.

PiperOrigin-RevId: 372572464

src/main/java/com/google/devtools/build/lib/rules/cpp/LinkBuildVariables.java

diff --git a/src/main/java/com/google/devtools/build/lib/rules/cpp/LinkBuildVariables.java b/src/main/java/com/google/devtools/build/lib/rules/cpp/LinkBuildVariables.java
index 2e928d7..55d0ef5 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/cpp/LinkBuildVariables.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/cpp/LinkBuildVariables.java
@@ -249,7 +249,8 @@
       buildVariables.addStringVariable(CS_FDO_INSTRUMENT_PATH.getVariableName(), csFdoInstrument);
     }
 
-    if (featureConfiguration.isEnabled(CppRuleClasses.PROPELLER_OPTIMIZE)
+    if (fdoContext != null
+        && featureConfiguration.isEnabled(CppRuleClasses.PROPELLER_OPTIMIZE)
         && fdoContext.getPropellerOptimizeInputFile() != null
         && fdoContext.getPropellerOptimizeInputFile().getLdArtifact() != null) {
       buildVariables.addStringVariable(