cmPropertyMap: Require a non-empty name parameter.

The cmGetPropertyCommand already checks for this.

Source/cmGetCMakePropertyCommand.cxx

@@ -52,9 +52,11 @@ bool cmGetCMakePropertyCommand
     }
   else
     {
-    const char *prop =
-      this->Makefile->GetState()
-          ->GetGlobalProperty(args[1]);
+    const char *prop = 0;
+    if (!args[1].empty())
+      {
+      prop = this->Makefile->GetState()->GetGlobalProperty(args[1]);
+      }
     if (prop)
       {
       output = prop;

Source/cmGetDirectoryPropertyCommand.cxx

@@ -84,7 +84,11 @@ bool cmGetDirectoryPropertyCommand
     return true;
     }
 
-  const char *prop = dir->GetProperty(*i);
+  const char *prop = 0;
+  if (!i->empty())
+    {
+    prop = dir->GetProperty(*i);
+    }
   if (prop)
     {
     this->Makefile->AddDefinition(variable, prop);

Source/cmGetSourceFilePropertyCommand.cxx

@@ -38,7 +38,11 @@ bool cmGetSourceFilePropertyCommand
       this->Makefile->AddDefinition(var, sf->GetLanguage().c_str());
       return true;
       }
-    const char *prop = sf->GetPropertyForUser(args[2]);
+    const char *prop = 0;
+    if (!args[2].empty())
+      {
+      prop = sf->GetPropertyForUser(args[2]);
+      }
     if (prop)
       {
       this->Makefile->AddDefinition(var, prop);

Source/cmGetTargetPropertyCommand.cxx

@@ -40,7 +40,11 @@ bool cmGetTargetPropertyCommand
   else if(cmTarget* tgt = this->Makefile->FindTargetToUse(targetName))
     {
     cmTarget& target = *tgt;
-    const char* prop_cstr = target.GetProperty(args[2], this->Makefile);
+    const char* prop_cstr = 0;
+    if (!args[2].empty())
+      {
+      prop_cstr = target.GetProperty(args[2], this->Makefile);
+      }
     if(prop_cstr)
       {
       prop = prop_cstr;

Source/cmGetTestPropertyCommand.cxx

@@ -29,7 +29,11 @@ bool cmGetTestPropertyCommand
   cmTest *test = this->Makefile->GetTest(testName);
   if (test)
     {
-    const char *prop = test->GetProperty(args[1]);
+    const char *prop = 0;
+    if (!args[1].empty())
+      {
+      prop = test->GetProperty(args[1]);
+      }
     if (prop)
       {
       this->Makefile->AddDefinition(var, prop);

Source/cmPropertyMap.cxx

@@ -14,6 +14,8 @@
 #include "cmake.h"
 #include "cmState.h"
 
+#include <assert.h>
+
 cmProperty *cmPropertyMap::GetOrCreateProperty(const std::string& name)
 {
   cmPropertyMap::iterator it = this->find(name);
@@ -60,10 +62,7 @@ const char *cmPropertyMap
                    bool &chain) const
 {
   chain = false;
-  if (name.empty())
-    {
-    return 0;
-    }
+  assert(!name.empty());
 
   cmPropertyMap::const_iterator it = this->find(name);
   if (it == this->end())