[LLDB] Fix inline variable only used in assertion. (NFC)

This prevents unused variable warning/error in -DNDEBUG builds. The
variable was introduced in 5934cd11ea3e.

Patch by: Shu-Chun Weng

Differential revision: https://reviews.llvm.org/D69451
diff --git a/lldb/utils/TableGen/LLDBPropertyDefEmitter.cpp b/lldb/utils/TableGen/LLDBPropertyDefEmitter.cpp
index 51c15a7..f36deee 100644
--- a/lldb/utils/TableGen/LLDBPropertyDefEmitter.cpp
+++ b/lldb/utils/TableGen/LLDBPropertyDefEmitter.cpp
@@ -46,7 +46,6 @@
   bool hasDefaultUnsignedValue = Property->getValue("HasDefaultUnsignedValue");
   bool hasDefaultEnumValue = Property->getValue("HasDefaultEnumValue");
   bool hasDefaultStringValue = Property->getValue("HasDefaultStringValue");
-  bool hasDefaultBooleanValue = Property->getValue("HasDefaultBooleanValue");
 
   // Guarantee that every property has a default value.
   assert((hasDefaultUnsignedValue || hasDefaultEnumValue ||
@@ -60,7 +59,7 @@
 
   // Guarantee that every boolean property has a boolean default value.
   assert(!(Property->getValueAsString("Type") == "Boolean" &&
-           !hasDefaultBooleanValue) &&
+           !Property->getValue("HasDefaultBooleanValue")) &&
          "Boolean property must have a boolean default value.");
 
   // Guarantee that every string property has a string default value.