Tidy up bug descriptions.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@64039 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/GRExprEngineInternalChecks.cpp b/lib/Analysis/GRExprEngineInternalChecks.cpp
index 76286f4..b7762d8 100644
--- a/lib/Analysis/GRExprEngineInternalChecks.cpp
+++ b/lib/Analysis/GRExprEngineInternalChecks.cpp
@@ -106,7 +106,7 @@
 public:
   BadCall(GRExprEngine *eng)
   : BuiltinBug(eng,"invalid function call",
-        "Called function is a NULL or undefined function pointer value.") {}
+        "Called function is a NULL or an undefined function pointer value.") {}
   
   void FlushReportsImpl(BugReporter& BR, GRExprEngine& Eng) {
     Emit(BR, Eng.bad_calls_begin(), Eng.bad_calls_end());